Need some clarification

[Celtic Fan]

I'm not the biggest fan of PER, but I always thought it would be useful in comparing players from the same era.

however when I see this it makes me question how much variance we should allow for in order to say what dictates a superior PER.
Take a look at Anthony Davis's numbers for this year and last. He's producing nearly the same stats except his FG% is .50 lower. That's a good dip, but should that mean is PER drops 6 points? I know FT, TO and APG are a tad worse but would those change a big's PER that much?

http://www.basketball-reference.com/players/d/davisan02.html

It just seems to me that those numbers don't warrant such a drastic difference in PER and if it does, then maybe I've (or we) have been looking at PER in the wrong light. I mean if a guy has PER of say 22 and someone else is at 18, could it just be a slightly better FG% and a half a TO less for the guys with 22? Is that really enough to say someone is that much better than another player?

[colts18]

Its a per possession stat and his numbers are down across the board

http://www.basketball-reference.com/pi/shareit/zqQGe

Usage, assists, stl, blk, FG%
his turnovers up by 1 too