CC for me - but I'm biased
Having had the CC for about 2 weeks now and driven to Coffs and back (1500kms all up), and visited my brother who just got an R36 sedan in January, the CC has a slicker interior/exterior with more comfort features (and the comfort setting on the suspension is really nice for long drives), aswell as the useful options of Park Assist and Adaptive Cruise Control - both of which I used pretty extensively. The front seats are more comfortable (according to my brother) in the CC because its all leather. Wife likes it more too. But my brother likes the harder suspension and definitely needs the 5 seats. Neither of us have really driven the cars hard during the run in period (mentioned in the manual) at 1500kms. They're the same engine so I don't expect huge differences.
However I have had a large (hopefully teething problem) in my CC - it leaks! During the heavy rain in Coffs, water pooled beneath the carpet in the drivers footwell area. Now its currently in the shop getting dried and the leak source identified. I hope this is not a bad omen - but for others buying this car, I would look out for this fault specifically as it may be an across the model problem (or not).