BMW does 80 stock and around 95+ after 2 upgrades. It's amazing and beautiful - it goes well in very many colours which I should know as I change my car colour 10000 times a day and it has nice body kits. I first bought it in 2014 then I sold it, then bought it recently and now indeed it is sold but I do really recommend it!
Both are good cars tbh, BMW is a really Nice car, one of My first cars, and I really though about buying the Mercedes cuz I like the look of it tbh, so if you want a good looking car, go for the E63, but yeah. Its still What you think so.
Mercedes- speed vs M3- beauty
For me it's looks>speed.
The Mercedes is ugly. cough @Robin Ljungberg
Oh, and there isn't a big difference in the speed, so you might aswell go for M3