I had the first version of the Ay-Ups and currently have a Trout Lumen Liberator. Both used on the bars and with a helmet-mounted Joystick.
Both lights are really well made and can do a good job with run times that I never really found the end of.
Obviously the Trout is way brighter than the Ay-up (although I think the newer ones are brighter than mine was) but I reckon it also gives a much more useful spread of light and has the bonus feature that it probably can also be used to cook food in an emergency situation! I liked that the LEDs of the Ay-ups could be independently positioned, easily provided enough light and are a really neat design but I did find that the bar mount wasn’t great, certainly not as good as the Trout.
Out of the two I’d pick the Trout every time but if I was buying again I think I’d go for an Exposure light just for the neatness of an internal battery.