One had a tendency to heat up and melt under sustained fire, then build up enough to cause problems like cases sticking. Once it cooled, it became a real PITA to remove the cases, if not impossible (well, close to imossible). I think that was the old lacquer. The new polymer doesn't seem to have this problem.
Now, that comes from from all sides, but mostly ammo snobs (I'll never shoot that Wolf crap in my guns) who heard about it on the internet and never once saw it happen, let alone ever shot a round of it. I've shot both, both in a 7.62x39 and my AR's. I've had no problem with either, although I don't have anything that shoots fully automatic. Am I saying it doesn't happen? No, I've seen the photo's of the stuck cases, scratched chambers from folks trying to pull the cases out (without the correct tools) and one guy with a destroyed rifle (Failed to extract, ripped the bottom of the case off, fed a new round into it and somehow fired....boom, destroyed the rifle). What happened up to the point of malfunction is rarely, if ever clear. Only the end result. Melted? Dirty chamber? Piss poor quality of a chamber or just plain stupidity? Usually no one ever tells of the "well, I never cleaned it, dropped it in the mud/sand/silt picked it up and fired it.....
I personally have never witnessed a single problem with Wolf (or any other lacquer or poly coated ammo ) other than it's a pretty dirty ammo to start with. I've shot several thousands of rounds of it (back when it was running about $100-125 per K) Remember, this lacquer coated ammo has been used for literally half a century or longer in the 7.62x39 with little reported problems. Maybe it's the relatively tight chambering of the AR? Maybe it's using 5.56 ammo in a .223 chamber or vice-versa....few variables to consider.
If you're shooting mag dumps, several thousands of rounds a day and keeping the barrel hot enough to melt platinum, stay with the poly stuff or brass cases. If you're doing a "normal range outting" where you'll run 1-200 rounds through in 2-3 hours, shoot what you want. And of course, it'll differ between rifles and calibers.
Just my opinion, I'm sure an expert will be here shortly.