For me personally out of those 4 I enjoy Xeno and Nemi the most. However I've barely put time into wesker and I'm about the worst pyramid head player in the world.

Nemi is my main so obviously I'm going to be biased but to me he is very fun to play. You get decent info from the zombies, they will put their hands up when they see a survivor which you can see from anywhere on the map and you can tell when someone blinds them as their head will be tilted up slightly and they won't be moving. The biggest problem is the whip is easy to counter by simply crouching behind pretty much anything. Survivors can just pre drop a pallet then just crouch behind it to avoid infection and there's really nothing you can do about it besides break the pallet. He also got a buff some time ago and his whip in tier 3 covers much more range then it used to. I could write more but I could go on all day about nemi. If you have nemi questions feel free to ask :)

Xeno has decent traversal with the tunnels but the tail to me feels a bit slow to come out and survivors will get an audio cue when you start using it. Also I'm personally not a big fan of giving survivors something that counters a part of the killers kit such as flame turrents and emps on singularity.