After experimenting a bit with upper/lower and push/pull 4-day splits, I have found a variation of push/pull that I've really enjoyed and spreads the burden more evenly across the two days instead of having a hard and and easy day:
Push Upper (Chest, Shoulder, Bicep) + Pull Lower (Hams) (A)
Pull Upper (Back, Tricep) + Push Lower (Quads, Calves, anything else leg) (A)
Rest
Push Upper + Pull Lower (B)
Pull Upper + Push Lower (B)
The main problem with U/L and P/P is that Upper and Push days tend to be much harder and involve more exercises than Lower and Pull days. And I hate to have two leg days a week on U/L. This split combines the hardest Upper workout with the easiest Lower, and then the easiest Upper with the hardest Lower. Also means your back didn't tire out on the day you might do deadlifts.
Anyone else do this? Any particular reason why this split is bad? I don't see any functional reason why you have to strictly do pushes or pulls for both upper and lower on the same day so swapping them seems fine.