It is common for cars running E10 fuel to be a little more difficult to start than they are on regular unleaded. Try unleaded and see if the problem persists. A rotten egg smell is usually a sign of a problem with the catalytic converter.

THE answer depends on the condition of the cars. Without knowing that it's hard to make an accurate call, but my feeling is the Camry has too many kays on it, the Leganza is too expensive and the long-term durability of Daewoos is unknown to a large extent, which leaves the Saabs. Of the two, I would go for the one with the lower kays, though there isn't much in it.

I WOULD be very cautious about installing LPG on the Leganza. It's not that it can't be done, and the engine might very well run happily on it, but my concern is that there is little history of Daewoos on LPG, so you would be entering unknown territory. I would recommend you call an LPG specialist, such as George Peake at Victorian Autogas Supplies (1800 620 945) and ask his advice.