There are what, maybe 3 people on this board who could throw down a faster lap in a CF vs. sunroof coupe - all other things being equal. You'd cut more time off a lap with a good set of R comp's than a roof ever could. It's an aesthetic choice much more than performance.
Before I bought mine, I did an epic 3 day drive through CA in a rented E92 with CF roof. Loved the car but several times every day, I wanted to pop open the roof to view the beautiful scenery. That was the deciding factor for me even though I love the look of the CF. Oh yeah, and I'm old