I think people are confused about the wheels, the car came with the deep dish 3 piece rims, I changed them to the CSL style wheels, which are an oem wheel and suit the car much better since it already has the CSL bumper and bootlid.
As regards which is quicker, A properly set up dc5 on sticky rubber would destroy my m3 in a twisty road at the moment, and probably have it to 60mph from a standing start aswel, but after 60 mph the m3 would sail away into the distance in a drag race, these m3's do 100mph in 3rd. They are a little heavier I'll admit, but they still have around 100 bhp more than a mapped dc5, and 3 times the torque.
However once I put on a decent set of tyres on it, and tighten up the suspension, the m3 should out pace a standard stage 1 dc5 in any scenario. after all, these are a 40-50k luxury super car, it's nice that they can be bought for 10k these days
As regards running costs, this is where an m3 lets itself down,
An oil change on a dc5 cost me about 45 quid doing it myself, for the oil and filter alone, it was 120 quid for the m3, Luckily I can do basic maintenance myself, but if you take your car to the dealership for every bolt turn, I wouldn't advise getting an m3.