He's far better than Mata. I'd go as far as saying Antoine is the best player in the world not at Madrid or Barca. His use of space, working of the channels and movement is some of the best in the game, if not the best. He gets one chance, he scores. Composed as feck, is good on the ball and can bring others into play. Not to add, having played under Simeone he will help out in defence etc. which Jose will take a liking too.
Doesn't really do fancy tricks or dribble 15 players but he doesn't really need to. He is almost always in the right spot to put the ball in the net.