to be fair, the M3 cabrio and the 330CI cabrio have differences
in styling as well like the flared wheel arches, power dome on the
hood, headlights, side vents, quad exhaust and diffuser, front
bumper etc....
but i would pick the S2000 if you enjoy tracking your car as its
lighter and hence handles better than the 330 round corners. 330CI
cabrio if you need 4 seats although i think all 4 seater cabrios
look like bathtubs.