Seems like an idiotic question given that you're comparing a car that is nearly 10 years older than the other.
Given that the US Cosworth is even slower than the euro spec unit, I'd rather have the m3. Larger aftermarket, superior chassis, better engines, loads of spare parts abound thanks to all the rich kids who wreck them on a regular basis. Shame the e36 is a less than stellar put together car on the inside.
With that said, I'm with Spectre, I'm going with "none of the above." I disagree on the XJR part though.
I'll stick with my daily e30 and my track miata. I get all the utility I need in a 4 door sedan and the superior performance of a better/cheaper chassis produced by Mazda. Added bonus, if I blow up my track car, I can still get to work the next day.