Bought a new E46 M3 drop top with Ac schnitzer zorst back in 03,now own a zed which again I've had from new.
Still miss that M car now as it was one of the best cars I've owned.
Putting to one side the technological advances made with cars since then this is my comparison( coupe) not conv.
1. Performance wise a standard Z wont keep up on track due to the power disadvantage but balance and drivability on the throttle they are on a par.
2.yes the standard brakes on the m3 are shocking!
3. Exhaust note of that strait 6 at 8000 rpm rasping away is intoxicating!
4. Interior/seating of the BM was second to none.but in the Z you feel your in a drivers car.
5. Looks are subject to taste as each car is classed as a coupe and they are both so different,( saloon based verses ,two seater)
6.If I was in the market with 6k to spend on either it's a tough call if you have no desire to modify.
7. Gonna keep my old Datsun till they put me in a box...