I would check ebay and autotrader(or the UK equivalent) and research resale values of the 3 series and the M3 cabs.
That would be my major consideration and a big reason why I bought the Boxster. Buying a car only to get 50% of its worth back in only four years is a faboulous waste of dough. The inexplicable part is that it even happens to car's that are rock solid in reliability.
One guy at my local Autocross club just changed careers and is now selling BMW's. You might want to drop your local dealership an email about which is the better investment since both meet your performance standards.
yeah black nice but no thanks, actually my last car was a black Miata, my friend had a black M3 tin top, and my other mate had a Black M5. We **ALL** bought silver cars, BoxsterS, 6 Series Cab, and a 500SL.
I'd get a silver one with gunmetal BBS RS GT's or the ultra light
SSR Comp wheel also in gunmetal.