incomparable. the new one is checkers. the old xcom is chess. it might seem overly detailed at first but when u get the hang of it, its quite quick. just check out some Lets Play and you'll see the difference. for example, there's no overwatch. your chars will roll for Reflex shot when its not their turn if they have the Action Points for the "overwatch" shot. "Overwatch" or reflex shot, is based off Remaining Action Points, reflex skill, and the weapon modifier (shotgun/pistol are 1.5x, hheavy guns are 0.5x, etc). Stuff like that.
It's completely action point based, for example, turn 90deg is 1action point, kneel is another 3, grab a clip out of backpack is 12, throw it to teammate is 40, the other teammate moving 8 to pick it up, grabbing from ground for 10, reloading for 12, and snapshotting for 18. Shit like that happens. Well, it doesnt happen but it could! Pretty awesome game.
https://www.youtube.com/watch?v=lLipckAHAI4&index=12&list=PLFds65xQmrDzbZrnCf2hC3X8F5FsrjaS-