The next 2 are the same flashlight with different light source bins. Not sure what that means, or advantages / disadvantages between the two. (Something to look into tomorrow, or if someone want to explain…)
i like the sanyo 2600mah batteries, they put out enough voltage to run the light at full power for most of their charge, while other batteries start losing brightness as they are discharged
The bins means efficiency, U2 is higher then T6, but you can’t get the 3C (warm white) tint in U2 bin, in U2 you get cool white which some people think is too harsh
If you like warm white (think incandescent lightbulb) then you can get the M1 in T6 bin, 3C colour
M1 is good, Dunno much about the UF models.
M2 I do not have, but I hear it is good too. A bit more throw than the M1, otherwise about the same output.