I've been using a rear flea (usually clipped to my jacket as a secondary light) since last christmas and I'm happy with it.
The usb charging means that it is sealed up and less likely to let water in, my mars 4 leaked at the seal and ruined the contacts.
Mars 4 was great for visibility but keep the receipt, I think they have a warranty (which I didn't keep).
I've been using a rear flea (usually clipped to my jacket as a secondary light) since last christmas and I'm happy with it.
The usb charging means that it is sealed up and less likely to let water in, my mars 4 leaked at the seal and ruined the contacts.
Mars 4 was great for visibility but keep the receipt, I think they have a warranty (which I didn't keep).
I'm considering one of these http://www.planet-x-bikes.co.uk/i/q/LISMRTR2/smart_lunar_r2_rear_light to go with the flea.