The frame is the big difference, the B5 is the original 350 frame. The C5 is an mid 2000 design. AFAIC, the G5 and B5s are the better frames. In fact, I wanted a B5 when I got the G5, but the C5s weren't in the shops yet. I bought the G5, which I was very happy with and B5s showed up two or three weeks later.
Bare