Well if you have battery drain issues with the S6/edge then it will give you better battery life for sure, but if you're like me with very good battery life then it's basically the same and so far my S6 edge is having the edge.
I hope it gets better but in the last 2 days since I got the G4 , on weekend where I get at least 6 hours of SoT on my S6 edge, on the G4 with same spps and settings is giving me 5.5 SoT, with an instance that I needed to recharge at noon yesterday since it was draining like hell, right when I writing my review that I posted in this forum, it drained about 20% in about 35 minutes. After that it has normalized, and yesterday and today I've got 5.5 hours.
Again, I hope that it gets better but as of now, the difference in battery size in favor of the G4 has meant nothing.