I upgraded from a m7 and I'm loving my g3 so far. If I decide to swap it for an m8 it's only for the dev support.
I'm 3 days into my g3 and battery life has been way better than my m7. I did root and remove bloat. Got 5 hrs of screen time with 30% left yesterday, never got close to that on my m7.
Any more questions about comparisons to the m7 feel free to ask