I've gone through two campaigns now and I'm beginning to realize that there are some benefits to some of the Chaos Realms, but I'm wondering now if that's incidental or intentional.

So going through them:

Slaanesh: Pretty obvious benefits. You get huge ass rewards if you take the deals. Simple con is that it will take you exactly 7-8 turns to get to the gatekeeper battle.

Tzeenech: I did think this one was just awful, but I've come around on it. It's probably the best place in the game for leveling up your units really fast. Islands have constantly respawning armies and all of them have a full heal here or there. If you aren't focused on getting the soul you can grind like crazy here, and killing armies will make solving the puzzle pretty simple too.

Khorne: It's just fast. You can potentially wipe it out in 2 turns if you run into the right combination of enemies. Other than that, I don't think it offers much.

Nurgle: Not really feeling this one. It's sort of like a gimped Tzeenech, with little armies and full heals. However, it's also constantly draining you, which makes me feel like its a little less reliable for grinding up.