hmmm - go and test drive both cars - twice: on a dry day and wet day.
I have an M3 V8 sedan (jb,dct blah blah tick every box). I love the car and am not regretting saying goodbye to my 335i. Some M3 V8 pros and cons imho:
Pros:
it is just so much fun! Summer evenings - you're in the car on the twisty roads out of choice
hit the throttle and welcome to the aircraft carrier launch (if the roads dry - if its wet well - hope u had full insurance
Cons:
V8 loves to drink - long-term ave. 15l
your pax will get a headache if u push the car
if it's wet or snowy, take some caffeine and join grandma in the slow lane - M3's like bambi on ice if you're too fast
Hope this helps.