I have three XM-L emitters, two of them are not driven very hard, one is a real hand-warmer. Pretty impressive light output, huge spill and big hotspot.
I also have a few XP-G's and one XR-E.
It is interesting that I keep moving the XR-E around to different lights because I like its output so much. It can throw as far as an XM-L with almost equal brightness, but without the big spill that lights up everything from my feet to my peripheral vision. Nice that I don't have to worry about wrapping it in foil, it seems to stay fairly cool and I can use 2xCr123 with it. I think it was $10 including shipping.
I think I'm going to have to change away from the P60 hosts and go to more of a thrower, I'm just not seeing the practicality of the P60 stuff with my XM-L's. If I was a cop or a firefighter, I guess they would be perfect, but standing in my back yard playing around with my lights (yeah, wife says I'm nuts) the XR-E is almost more interesting with its more defined beam.
My XP-G dropins seem to project in a very similar manner to XM-L's, just not quite so bright. I really like the XP-G emitters that are in most of my AA sized lights, in the P60 sized they do fine, but maybe I am too hard to satisfy. No WOW factor, unless you are used to a Maglite. I guess what I really like in a flashlight is predicated more on the body and reflector than it is on the emitter.
<rant over>
BTW, one of my XP-G emitters has a very noticable green tint in the center of the hotspot if you project it on a white wall from 3 feet away. Is that something you've seen in your XP-G?