Well, the ARC (which you know about) is a great little light. I have one stock ARC-P that is great, though it is "just enough" light for most dark indoor tasks.
I have an ARC that was customized by "millermods" at CPF with a Cree led, running with a very low level (about same as stock) and then 350mA on high....it's fantastic, but I think it cost me over a hundred bucks. Arc also just came out with the next level up in theeir lights, still only promises 9 lumens (likely more like 11, though). Still,it's a 5mm with crazy runtime, sufficient for "emergency lighting")
The other keychain has the Fenix LOD-CE with the cree that first came out in them, so probably a P bin. It is a great little light. It looks a little beaten up (as compared to he arcs that look BRAND NEW). But it is just as bright as ever. A nice usable low level (about the same as the stock ARC-P, I think), a solid mid level, and a pretty impressively blazing HIGH level. I run regualr AAAs in both lights. I got the blac color, a better coating might keep it looking nicer. It's been on my keys for over a year.
For the money, I don't think there is a brighter and more versatile light. There are of course th DRAKE, Draco, and WEE (from Lummi) out there....they are insanely bright andinsanely cool. The Wee is my favorite right now. 30 minutes of 50 lumens on a tiny rechargeable out of a flashlight that s smaller than a single CR123 battery. With the "goodies" and a charger and tritium it'll run you a hundred-ish bucks. For an extra 20 bucks you can also get the lower emitter (25 lumens--1.5 hours runtime) or the brighter one (80 lumens, 15 mintues runtime).
An other questions, or if you want opinions on other things, feel free to PM me.