#1 Ditto
#2 Again always highly subjective. There are half a million comparisons out there. I don't think you would notice a difference in cpu speeds, as for the screen, they are pretty different. AMOLED is awesome with its true blacks and brightness. Despite the grain, I loved my LG Flex's P-AMOLED display. On the flipside however the colors are vibrant and inaccurate. At the same time that true black and brightness are something to behold, it is equally impressive to know that your display has some of the most accurate color production you can buy as is the case with the G4. Also if you browse with the lights out like before or after you sleep, AMOLED does not have a very low brightness setting. I found %0 on my gflex still hurt my eyes, the G4 on the other hand can drop to a brightness so low that it is very hard to see under normal lights.
#3 since the most recent lollipop patch, battery life is amazing, as good as my LG G Flex now I have to run around with cellular turned off half the day because parts of my work are in dead zones and I found they would drain the battery, but with wifi/bluetooth (moto 360 watch) active all day Ive been putting it on the charger anywhere between %76 to %60 on a normal day when I go to bed. I have a Battery stick just incase but the only time I needed to use it was when I discovered I was in a dead zone mentioned above and by lunch my battery was %20.
#4 cell signal seems alright, I think my g flex did a little better (G4 on verizon can roam on sprint, what my flex was on. Flex never had an issue with staying on sprint and yet in some areas of my store the G4 can't maintain sprint either). Wifi also seems to have taken a step down as the wifi at work is a few bars shorter than what my g flex saw on average. This has no impact at home however, they both get good signal to the property line.