Went from Gs6 to the G4 due to two things: battery life and lag.
The lag wasn't crazy slow but it was there and it was annoying. It just couldn't handle how much I use the device.
Now, the battery life on the GS6 was terrible. Very terrible. With my usage, I would unplug at 9am and I would be at 0% by 3pm. Maybe sooner. So I had completely charge from 0% about twice a day. Very annoying.
The G4 doesn't have the battery issue, and I have noticed maybe 2 times that it has lagged. My battery now lasts me all day so I don't ever need to plug in during the day.
What I don't like: build quality is definitely better on S6, and I actually much prefer touchwiz on the S6 than the LG skin. I really don't like the LG skin actually. Especially what they did to notifications.
When the S6 is running smoothly, it was also faster than the G4, but unfortunately it has lag. If the S6 ran like new all the time, it would be faster than the G4. I usually like to increase the animation and transition scales from 1X to .5x, which I did on the S6 and worked fine, but the LG G5 cannot handle the increased speeds. It lags immediately. So I just left it alone and it performs fine.
Honestly, if battery life was better on the S6, I would have dealt with the lag it had here and there. I really loved that device. But the battery life was just way too annoying for me.
Posted via the Android Central App