Well there is literally no assistance on PS4. Seems to be knackered and can see the difference in those who it's probably working for -.-
Its useless with shotguns, because if you're doing shotguns right you're probably playing lockers, where it messes with your target prioritisation and will drag you in the direction of the guy at the bottom of the corridor, not the one two foot in front of you but right at the edge of your FOV !
I find it easier just to turn it off.
I don't find the aim assist on xbox one that much of a help tbh.
Some people make out like its an aimbot, in reality its nothing of the sort and just gently shoves you in the direction of a person who runs across your field of view. It won't track a target for you, just point you in the direction the person went.
Get up close behind people to give them as little time to react as possible. You also need to aim as best as possible as they will only hit if they get near them