This answer is based completely on my experience with Mercedes and BMW. I don't like BMWs at all. I think they're gaudy and in San Diego, everyone drives them. I know they have a decent maintenance package, which can be helpful, and Mercedes does too. Free scheduled maintenance for 2-4 years depending ont he model. Since that car will be used, neither will have the maintenance package so it comes down to reliability.

I currently drive a Mercedes ML350 and I know its a different car from the C300(which I love), but I'll give you my general experience with Mercedes. They are expensive to fix, and have a lot of issues. Ours has had the brakes replaced 3 times in 3 years and the alternator replaced within the first four years. It's had a number of electrical based problems and had one we couldn't even figure out for a while that would occasionally just leave us stranded. It turned out to be an electrical problem that cost us $1100 to fix.

In any case, although I hate BMWs, they are cheaper to get repaired(at least in SD because of the prevalence of them and repair shops), slightly more reliable. They do not look better or drive better necessarily, although some have said they handle much better than Mercedes(including Car and Driver).

I would just buy an Audi, personally. They are great cars and last longer. Either that or a Lexus. Lexus don't have the same horsepower or prestige, but they have nicer interiors, more luxury, and the durability of a Toyota, since they are made with the same parts as many Toyotas. Even when they weren't owned by Toyota they were reliable. I used to drive a Lexus that had 370,000 miles on it and that was still the first engine.

Anyways, good luck in your search.

It's certainly a personal preference. The BMW 330 in my opinion handles better, and factually it's better on fuel economy. If you're looking for performance go with the bimmer. These ultimate driving machines hold up well beyond four years.