I’ve been fairly happy with the Blaze 500 on group rides, by I do wish it was a littpe brighter. I’ll probably decide tonight if I go on the group ride if I want to exchange it for the 650
Honestly, I don’t know if I’ve ever used it riding. I take it along as a spare. It’s plenty bright, though! Still working, and I use it as a flashlight on a regular basis. 
I’ll have it tonight if you want to give it a try. The most negative thing is that the helmet mount in very basic. It’s just a rubber pad - no tilt adjustment, so it might take a little fiddling to get the light pointed where you want it, and then you’re stuck with it in that position, unless you adjust the strap.