2018 BMW X3 vs BMW X5

What's the difference?

BMW's 'B58' six-cylinder engine is what's known in the trade as 'a cracker'. Three litres and a turbo's worth of silky smooth power, it delivers big dollops of torque with the kind of immediacy once reserved for much larger units.

It's already a perfect match for the M140i hatch, as well as the M240i coupe and convertible. And once you hit on a winning formula, why not spread the joy into the ever-growing world of SUVs?

Enter the X3 M40i, the first performance variant in BMW's compact SUV range, sitting just under $100k (before on-road costs) and aiming up at a quality field of similarly sized and specified performance versions like the Audi Q3, Jaguar F-Pace, Merc-AMG GLC, Porsche Macan, and Volvo XC60.

Favoured by everyone from governments requiring bullet-proof security vehicles to parents doing the school drop-off run, BMW's X5 is the limo of the German maker's now extensive SUV range, and the xDrive40d sits close to the top of the line-up.

As if that's not enough pressure, the X5 is up against fierce rivals in the form of the Mercedes-Benz GLE, the Porsche Cayenne and Range Rover Sport.

You'd expect an X5 to be luxurious, come loaded with advanced technology, and be dynamic, because it's a BMW, and that's the brand's shtick. But it's an SUV, so it should also be practical.

That's a lot to ask, but after living with the X5 xDrive40d for two weeks, it gave me the answers.