you might want to check with your insurance co about the difference between the rates, could be significant? i'd say go with the M first all other things being equal, but they aren't. they are totally different cars, not just engines. the M comes with better brakes, wheels and tires, different body, front and rear facia, interior trim, sound and rollover protection to name a few. with all the upgraded M equipment comes slightly upgraded maint/operating cost, but also more aftermarket availability.