MTB Bike Light geek warning
There are several corners to the MTB light design space, having some idea of the tradeoffs can help the buy decision.
Ayup concentrates on selecting the most efficient single (expensive) LED emitter, with the best match to some very efficient optics and matched to power supply and battery voltage to minimise the battery size and/or maximise battery life and provide the best beam pattern. All this optimisation comes at a cost.
Everyone I know who has them loves them and Ayup support their customers with a refurb service to give your old Ayups new more efficient emitters.
At the other end of the design space is the "I don't care about the beam pattern or efficiency - just get some big numbers" use a multi emitter single module, drive it hard and keep the costs down.
In the middle somewhere are the triples and quads. These suffer a little efficiency penalty from the optics you have to use to stuff them into a small enclosure. I can easily notice the difference in brightness of a 35mm triple and a 20mm triple optic. In the same enclosure a triple could "look better" than a Quad. To be able to use the compact internal reflection optics, the triples and quads also use the same types of emitter as the Ayups, but maybe less expensive/efficient/brightness bin parts.
If you can only afford the cheapies and this the difference between doing the ride or not then the choice is obvious, go the cheapies! Be prepared to do some DIY replacing the battery about a year down the track... by then you will know enough about what you really need.
If you have trouble sleeping, you can spend hours in here (I have - can you tell?)
http://forums.mtbr.com/lights-diy-do-yourself/
and spend your cash here;
http://www.cutter.com.au/
FYI - I use DIY triples - a few of us did a production run of ~20 at the place I work. I've used 'em for 3 years of commuting, a 3 ring circus and a Mont24 - all good.
- carpetrunner