The UI. Oh, oops.
The battles are a lot less time consuming and more interesting to look at. Also, the simultaneity makes them more understable, to me (I couldn’t quite compute the timing at which things were happening before). I feel like I have a better grasp over them, but I wouldn’t be able to tell you if it is based on perception, or mechanics.
I also only play single player because I am a cryptozoologist, not a theologist.