I prefer the Cycleaware Reflex mounted on my helmet. Glasses mount only works if you don't have very thin temple pieces on your glasses (otherwise they won't stay put) and when I was using glasses mounts I was always forgetting them. On the helmet they're just always there.
I used a Take-A-Look and it works well, but when I got into an accident the sharp edge of the mirror and the stiff wire right near my face caught up to me to the tune of about 18 stitches. The Reflex is all padded and rounded and is even more adjustable.
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Work: the 8 hours that separates bike rides.