Lexus Rx450H+ vs Mercedes-Benz SL-Class

What's the difference?

The new Lexus RX450h+ Sports Luxury is packed with a wealth of premium features and strikes a solid balance between refinement and practicality. There are enough thoughtful touches that make everyday driving a little easier.

You’ll get the most out of the plug-in hybrid powertrain if you’re able to charge it regularly; ideally every day. That might not always be practical for busy people on the go, but overall, the RX450h+ manages to blend efficiency with Lexus’ signature comfort and quality.

The SL's overall score is somewhat skewed by everyday concerns, and rules are rules - an average punter will find the price of this car somewhat confusing and the devil-may-care attitude to fuel consumption bewildering.

If neither of these things are a problem, then the SL63 makes plenty of - well, not sense, because it's not a particularly clever or considered car - but it fills a niche that not so long ago we all thought would go the way of the dodo.

The fact it sells so few examples is betrayed by some of the cabin amenities and the fact that Mercedes hasn't put much effort into reducing the car's weight to improve its consumption or sharpen up the handling.

The fact it still exists at all is pretty damn cool, though, and for certain people an SL63 purchase is the culmination of a lot of hard work.

If it is your dream car, the SL63 won't disappoint. Everyone who rode with me said it was mightily impressive, but you've got to really want it. When you're not far off buying a Ferrari California T or Aston Martin V12 Vantage S for the money, you'll need a real yearning for the three-pointed star to go this way. And if you do, good luck to you - you've probably worked quite hard to get here.

The RX isn’t breaking new ground with its plug-in hybrid design, but it still delivers that signature Lexus understated refinement.

The strong, flowing body lines, 21-inch alloy wheels and updated 'spindle grille' all give it presence without screaming for attention.

And in a segment where boxy and bulky designs tend to dominate, the RX’s swoopy silhouette helps it stand apart in all the right ways.

Inside, the cabin feels considered and luxurious. There's a heavy use of premium materials, including the leather and suede upholstery, plush soft-touch surfaces and the big, crisp displays that make the space feel modern and high-end.

The panoramic sunroof brings in loads of natural light, too, which is especially welcome given the dark headliner that might otherwise feel a little heavy.

If I have one gripe, it’s the thin steering wheel, which doesn’t quite match the otherwise solid, tactile feel of the rest of the interior. But overall, the cabin is a space that feels luxurious and well-executed. It's quietly confident, just like the RX.

The SL has always been completely unapologetic about its size and seems to be designed to accentuate rather than hide its length and width. The long bonnet screams power and prestige, and get out of my way, and is reminiscent of the little-loved McLaren SLR project of some years ago.

The size of the Mercedes logo on the huge front grille leaves you in little doubt about the brand of car that’s about to pass you at speed and some might say (okay, I would) that its large surface area is a little vulgar.

Like the SLR, the design doesn't seem to have a particularly cohesive strategy, with a number of Mercedes elements from around the traps that climb over each other. Roof up it looks awkward because of the gigantic posterior while with the roof down it looks overly long and, again, tail-heavy.

Folding hardtops are notoriously cumbersome and need a lot of room to hide them, but the silent operation is something to behold.

Elements that are worth deleting if possible are the dodgy 'Biturbo' badges. It's that kind of bling that gets people raising their little finger at you.

The RX cabin is thoughtfully laid out and impressively practical, with a premium feel that doesn’t come at the cost of everyday usability.

Up front, there’s plenty of space for driver and passenger, yet the stepped dash design brings a sense of intimacy. The electric front seats are seriously comfortable, with four-way lumbar support and extra adjustment functions that make this an easy choice for long drives.

Storage options are generous, too. There’s a clever dual-opening centre console, large glove box, multiple phone-sized shelves, map pockets and a couple of cup- and drink holders in each row.

Charging is taken care of by four USB-C ports, one USB-A port and a wireless charging pad.

Tech is up-to-date and well-integrated. The upgraded 14-inch media display looks crisp, supports wireless Apple CarPlay and Android Auto, and is paired with a revamped 12.3-inch digital instrument cluster and a colour head-up display.

The cluster’s new layout is modern and much easier to read than the previous offering. The digital rear view mirror also earns its keep when the cabin’s packed with passengers or gear.

One of my favourite touches? The seat controls on the side of the front passenger seat. It makes quick work of moving the seat forward, especially helpful when you’ve got a kid clambering in with a school bag full of projects.

Access to the rear row is easy, but the stadium-style seating, where you're perched noticeably higher than those in the front, won’t be for everyone.

That said, the rear seats are plush and padded, though they lack side bolsters, which rear passengers might notice during cornering.

Legroom is generous and the hardened kickplates are a dream to clean when your child’s treating the seatbacks like a climbing wall.

My eight-year old gives the back seat a glowing review, thanks to its creature comforts, including rear climate control, directional air vents, seat heating/ventilation on the outboard seats, two USB-C ports and retractable sun-blinds, which are a crowd favourite in our household.

There are three top-tether anchor points, and the bench is wide enough to fit three child seats, though bulky booster seats might be tricky due to the raised seating height.

At the back, the boot is well set up for families, offering electrically folding rear seats, a 12-volt socket, flat loading floor, and a hands-free powered tailgate.

Under the floor, there’s a small compartment for your charging cables (Lexus throws in two!) and a usable 612L of capacity when all seats are in use. One downside, though, is the lack of a spare tyre as you just get a tyre repair/inflation kit.

“Practicality” is about as relevant to this car as a code of ethics is to a drug dealer or a contract killer, because the SL63 buyer is hardly worried about cupholders and boot space. For what it's worth, there are four cupholders in the two-seater cabin (which might explain why owners aren't worried about their liquid carrying prospects) and a minimum boot space of 364 litres and a maximum - with roof up - of 504, which is actually not bad.

Cleverly, there's a little robot-operated luggage cover inside the deep boot that stops your gear from being crushed when the roof goes down.

There's also space in the long doors where you might secrete a bottle of wine that would get a NSW Premier fired if he thanks you for it, and a bin in the console to hide your phone.

It’s difficult to ponder the idea of value when a car is already approaching $400,000 at a rapid rate even before you start piling on the options. On the plus side, for a list price of $368,715 you do get an extremely long list of standard equipment.

The SL has always been completely unapologetic about its size.

Edited highlights include leather on almost every available surface, heated and cooled electric seats with a fan heater for your neck, a B&O stereo that will shatter the windscreen on request, aluminium trim that's real aluminium (mostly), Active Ride suspension, sat nav, dual-zone climate control, active cruise, LED headlights and a huge swag of safety gear.

The 12-speaker stereo also has DVD, limited smartphone integration via Mercedes' COMAND system, a seven-inch screen and, of course, Bluetooth.

Under the bonnet the RX450h+ Sports Luxury runs a plug-in hybrid powertrain that pairs a 2.5-litre four-cylinder petrol engine with a CVT auto and dual electric motors - one on each axle. Together, they produce a total of 227kW of power, though Lexus doesn’t quote a combined torque figure.

Still, it’s quick off the mark for a large SUV, with a 0-100km/h time of 6.5 seconds. There’s more than enough grunt for daily driving and overtaking, even if it doesn’t quite match the outright power of its key PHEV rivals.

The SL63 is powered by Mercedes’ increasingly famous V8, with two turbos along for the ride to add oomph and cut the car's famous consumption, at least slightly. The 5.5-litre unit produces a massive 430kW and a scarcely believable 900Nm of torque.

All of that heads rearward via a seven-speed dual-clutch transmission that helps sling the 4.6m, 1848kg machine to 100km/h in 4.1 seconds.

The plug-in hybrid system brings solid efficiency, with claimed fuel use of just 1.3L/100km. In real-world conditions (mostly urban driving with regular recharging) I managed a respectable 4.8L/100km, which makes a strong case for the hybrid set-up.

The fuel tank holds 55 litres and it's worth noting Lexus recommends using a minimum of 95 RON unleaded petrol to fill it.

Using our real-world economy figure you can expect a range in excess of 1100km between fills.

The RX450h+ is fitted with a relatively small 18.1kWh lithium-ion battery, supporting an NEDC electric-only range of up to 65km.

While that’s fine for short daily trips, it’s shorter than you'd ideally want in a family SUV of this size and it lags behind rivals like the BMW X5 and Volvo XC90 in this department.

Charging is simple enough. The RX uses a Type 2 charging port and accepts up to 7.0kW on AC power, which means a full charge takes around 7.5 hours, perfect for overnight top-ups. Lexus also includes an at-home charging cable and second adapter cable as standard, which is a thoughtful touch.

Much as is the case with the price, there's no real way to soften the blow here - the SL63 drinks like a footballer on Mad Monday, except it does it every day. The official combined cycle figure of 10.2L/100km is quite easy to double, as we did, averaging 21L/100km in mostly flowing suburban traffic. In the car’s defence, the accelerator pedal spent a good deal of time near the firewall.

The SL does have stop-start to help reduce its considerable environmental impact.

The RX450h+ delivers power that’s pert and prompt, with genuine bursts of acceleration that make driving fun. It’s always ready to go and there's no lag in stop-start traffic - which gives it a lively, dynamic feel around town.

The transition between petrol and electric power is seamless; you hardly notice the switch, which makes for a smooth, refined driving experience. The cabin is impressively quiet, even on the highway, making long trips comfortable and peaceful.

Regenerative braking isn’t adjustable and is subtle enough that many won’t notice it which is likely a plus for fans of traditional internal combustion engines who are making the PHEV leap.

The adaptive variable suspension adds a sporty edge to handling, letting you confidently take corners at speed. There’s some body roll but the RX never feels top-heavy or unsettled.

The steering carries the weight of the SUV but remains well-balanced and responsive. Overall, it’s a well-tuned machine that’s a pleasure to drive.

Maneuverability is a strong suit, too, thanks to a tight 11.8-metre turning circle and a clear, easy-to-use 360-degree camera system. Parking is easy-as-pie, which a lot of drivers will appreciate.

There are a number of impressive things about the way the SL drives. Firstly, astronauts will be familiar with the galactic thrust of the V8. It seems endless, seamless and ready to sling the big coupe into the outer atmosphere. Few engines of any kind can match the relentless go on offer in the SL and much of the credit should go to the seven-speed twin-clutch transmission.

When you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops.

Containing a torque figure like the twin-turbo V8's requires a lot of electro-trickery to stop you from being launched off the road. The great thing about all that stuff is that it works unobtrusively and smoothly.

Mashing the carpet in an SL without traction control would create much sound and smoke but little forward progress, such is the twist on tap. The SL has a range of modes from full-nanny (which is meant to keep you on the slippery Alpine road you've chosen to get you to some Swiss ski resort) while turning the dial all the way around to Race loosens the bonds.

It's in this mode you'll have the most fun and it does seem that the intermediate settings are a bit of a waste of time. Race mode does little to diminish the amazing ride quality provided by the active suspension setup, but relaxes the reins on the huge rear tyres. Exiting roundabouts is suddenly a huge laugh, with the tail cheerfully breaking traction and the two-mode exhaust thundering in a most pleasant way.

Better still is that when you jump on the brakes and shift down, the exhaust keeps the show going with angry crackles and pops, with more on the way when you lift off. There's little to match the aural pleasures of a properly tuned V8 and Mercedes has resisted the temptation to quieten it down on the outside and generate a fake noise for the inside. Although that would be stupid in a convertible, if you think about it.

The SL63, despite its AMG badge, isn't about all-out handling, of course. The Ferrari California would definitely show it how it’s done on a winding country road. The SL is more about flow, building momentum and rarely shifting down to second gear. The monstrous torque is enough to keep things rolling but should you wish for a bit more of the exhaust bellow, second is there for the taking.

Hustling the big convertible feels wrong, not because it can't do it, but because it's not really what it's for. Having said that, it offers a kind of fun that nothing else on Earth will provide, not even a Bentley GTC.

With the roof up, the SL63 is a quiet place but not remarkably so. The huge sticky tyres do the cabin's hush no favours, with an annoying roar on a wider range of surfaces than you might expect.

Roof down, it's hardly a paragon of virtue. A lot of wind noise reaches the cabin, even well below the huge speeds the SL can reach. So if you want to talk, it's windows up you'll need to deploy the mesh screen that bridges the roll hoops.

Six airbags, ABS, stability and traction controls, blind-spot sensor, lane-departure warning, brake assist, active safety bonnet, lane-keep assist, driver attention detection, AEB.

The RX comes with a five-year, unlimited-kilometre warranty, which matches its key rivals but isn’t exactly class-leading by today’s standards.

Servicing is handled via a capped-price program, with each service costing $695. The intervals are well spaced at every 12 months or 15,000km, whichever comes first.

This Sports Luxury grade also includes a three-year complimentary 'Lexus Encore' membership, granting access to a handy phone app and member benefits at partners like Westfield and Ampol. On top of that, you get 24/7 roadside assistance for added peace of mind.

The SL63 is covered by Mercedes' three-year/unlimited kilometre warranty. And, er, that's it.