As promised, here are the photos I borrowed from the Net some months and years ago, so I cannot remember all the credits, but I will happily do so on request.
The 8C is most round, more sensual maybe, than the 4C, which doesn't mean that I wouldn't choose the 4 C over the 8C.
From what I've been told, or from what I cold read here and there, if you want to have fun on a track, then the 4C is more joyful to pilot. If you are more after a GT, then the 8C is the one.
The 8C is almost twice more powerful, but it is much heavier, too. But it has the incomparable melody of a 8 Cylinders.
The photos, now:
Enjoy,
Nicolas