I've got a 6P and a G2. I think the difference is aethetics; maybe the aluminum body is tougher, but in the real world I don't know how you'd tell.

Because of limited battery and module life, I also carry a Inova X-0 in my FatBoy. Very nearly the same output. I also use an Inova X-5 for EDC. The quality of the light of the LEDs takes some getting used to.