I voted for the Arc AAA-P. I have one and I use it AAALL THE TIME! Personally I don't carry mine on my keychain; I carry it tied onto a carabiner which clips to my beltloop. The light sits in my left back pocket of my jeans, and I never know it's there. This way, I actually always have it with me as long as my jeans are on. People say, "Put in on your keychain so it is always with you"...well, I don't know about you, but I don't walk around the house with my keys in my pocket. I've also read a lot about people carrying the AAA-P around their neck, so that it's always with them...another option I might try in the future. Either way, the Arc should be with you at all times. It's too small not to carry.
I don't own an L2P, so I don't know much about it's durability, but my AAA-P has taken some nasty falls onto tile and concrete. I've picked it up, sure that it would be broken and it has always worked.
This light puts out enough light for everything indoors as well as many outdoor activities. Don't expect it to blow you away in the lumens department because that's not what it's about. Like others have stated, this light is about dependability and long runtime. That's what I like about it. I like knowing that I can grab it off my beltloop, give a quick twist, and in return it will give me light. There's no hoping I didn't break it, there's no hoping the battery isn't dead, there's no hoping it didn't get wet inside.
Well anyway, I'm rambling now, but you get the idea. The Arc is the way to go.
Edited for grammar
--AaronA