The Arc AAA can't be beat for overall function and cool-factor. I've got an LE (now called "Premier" or something) and my wife has a standard white. Hers actually saw her through the big blackout in Manhattan. All her co-workers now think she's Mrs. James Bond.
-Get one, then get a kydex sheath from Eric at On Scene Tactical. It lets you carry the Arc on your keychain, but remove it and use it separately. Nice.
I don't have a G2Z, but I do have a Z2, so six in one... I love it and carry it at work. It's everything you expect from SF, bright, tough, etc. The only downside to the combatlights is that the rubber grommets that define them make them VERY difficult to get in and out of the Surefire holder (V70.) And the Surefire holder is the only one wide enough to fit them (because of the rubber grommets!) The Nitrolon version may be a little easier, but I doubt it, because of the... well you get the idea.
If I had to replace it tomorrow, I'd buy a 6P just to be able to use standard holders. Size and brightness are the same as my Z2. If you're set on Nitrolon, the G2 is good, bright and cheap, falling short only in the lack of a lock-out tail cap and a pyrex lens. Important features to be sure, but could one live without them? I'd say so.