C-12 will work much better due to the fact thats its distilation curve is much better suited to the requirments of a bike engine. Red will work, but you will give up throttle response and overall performance.
I agree with BWalker, sometimes the local shop only has red available and the throttle response is alot different than with the c12, it almost feels the same as sunoco 94 down low. In my opinion the c12 is well worth the extra $$.