Now that weather's in, I think alot of our opinions will change in terms of serious racing vs. casual track days.
Due to the crazy handicap you get in cockpit view, I'll be more than happy to use bumper cam for time trials or serious racing. When it's pouring or snowing, it's going to be mighty tough to see how far ahead my opponent is in front of me, which leads to more unintentional punting. So for some clean/serious racing, Bumper Cam. For mucking around and just driving around the track for fun, cockpit cam.