The 328i definitely feels faster and a bit more fuel efficient. I personally prefer the 328i's feel ("comfort" or rather stiffness).
The c300 "sport" has more useful power in terms of regular daily driving. It's much more comfortable and you don't really feel the car needs much effort to pull mainly because of the 7sp Auto and the much higher torque it has.
I've only been able to push my 328 and not the c300 because the c300 isn't mine and I won't do so unless the owner was with me in the car and gives me the go signal to do so. I'll tell you now, neither cars were meant for racing...they're just not at that level (not to mention the lack of modding options for both cars).
It's all up to preference...