M3 all the way. I got a e39 2.8 it's big, it's heavy. It's not a fun car.
think the m5 will be a wee bit diffrent to a 528i
It is a lot different, gets about the same fuel economy if the person driving it is not driving like a hooligan, but honestly there isn't much chance of that!

it's still a heavy car though so doesn't handle like an M3 does, but still handles very well and still likes to get sideways with the traction control off, M3 is quicker through the corners but not as fast on the straights, but both have enough power to satisfy as far as speed is concerned and both will kick their ars3's out if you want them too.
4.6 V8 MG ZT would be fun if you can find one, 500 hp supercharged ford V8 + rwd = very sideways, very fast and very unpratical!
