Deciding between this and the Xeno for the Nichia 219... leaning towards the Xeno unless you guys can persuade me!
Here's some info to chew on; not necesarily pros or cons:
L10
Smaller, especially when carrying in a pocket
Nicer beam IMO (a bit more flood but still useable throw)
Available clip for about $2, but comes off easily. More of an anti-roll device for me.
Can use 14500, but get's hot and many don't fit well. Needs to be a button top.
Many people don't like twisty heads; very annoying if you use high mode alot.
Xeno E03
Sturdier but much larger
Beam has more throw
Better 14500 support and fit, but all three modes are close in output. Definitely lose a useable low mode.
Reverse clicky, hidden strobe (3 fast clicks while on)
Overall, I think the L10 wins due to the small size and price