The "vs." question is really all about usage (IMHO).
I own:
A Photon & ARC AAA & Infinity & Infinity Ultra.
For keychain use...it is the Photon or ARC AAA.
For 1 minute use per day, you'd change the Photon batteries about once every two years. For this sort of occasional use, I think the Photon is great.
If you are using your keychain light a lot more than this (3-4 hours/month?) you'll likely want the ARC AAA 'cause the batteries will be so much cheaper.
If you are camping, walking, night sky observing, etc. and long life means a lot to you, you'll likely want the Infinity Blue-Green (30+ hours on 1 AA) or the Infinity Ultra (6+ hours).
The Ultra actually is brighter with a broader beam than the ARC AAA (although, if you just look at the hot spot...they seem quite similar). Either Infinity is great for using up "spent" AAs from other lights. Some people on the forum report never actually buying AAs for their Infinites 'cause they have a steady supply of used AAs from some other source.
Also, a lithium AA is a nice option too (cold weather and shelf life).
If you are only gonna buy one >shudder< you CAN'T GO WRONG by buying the ARC AAA.