Red or Blue? The question has no right answer for everyone. I haven't tried the handle bar mirrors, but I also knew I was using more than one bike for commuting and I didn't want to have to buy and adjust multiple mirrors. As such, I opted for the helmet mounted mirror. On the rare occasion that I ride without my helmet (when I visit my parents and we go for a stroll on the residential side streets) I miss having the mirror, but I do like it so much that it almost forces me to wear my helmet (as if I needed reasons beyond my brains being splattered on the pavement).

So, I say check out a couple, see if you can test them. Do note though that the helmet mounted mirrors do seem to take a little getting used to and some finagling. It took me about a week to find the sweet spot for where it works well, but I love it.