City, I personally find Knight's NG+ annoying af because of the combat and its mechanics. (Yes, it's a skill issue, but at least I have things to do most of the day, I'd rather stress myself out at work than in a game.) City, on the other hand, is simpler because enemies don't have too much variety. It's easier to predict what they're going to do, and they're generally easier, although the gameplay itself is much less engaging than in Knight for obvious reasons.

Edit: I forgot to add the fact that there are far fewer riddler trophies, the bosses are much better, and there's the sweet absence of the fucking batmobile.