The U2 is very different.
First thing is size ... although not that apparent in pics, the bigger head and diameter play a huge role, depending on how you tend to carry your light.
The U2's increased throw has a significant impact outside and is well worth it if you wanna use the light outdoors, and the 6 levels add basically runtime which is important. The U2 has a more all-around beam and excells in every situation for a light in this class.
The L2 has one big advantage: momentary high. A very convienient feature. IMHO.
I would chose the U2 over the L2 ... but ... to be honest ... I carry the L2 as often as the U2 for simple size considerations.
Both are great lights.
bk