I've had both on my car, B's first and now C's. I greatly prefer the C springs. The B's made the car feel almost soggy yet harsh. The C's, in concert with 03 Cobra Bilsteins, seem to offer a much more solid feel all around.
Also, with the B springs, -1.4 degrees of camber was a positive as I could get it. With the C's, I have it at -0.6, but I have a full range of adjustment.