Mata, as yet, though he has plenty of games he's poor. There's a reason all three are in the EPL and not at Real or Barca. Silva is inconsistent and frequently poor against bigger teams, can't impose himself on a game where a Fabregas/Xavi shine in games like that. Mata is far less inconsistent than Silva and seemingly more effective but he also takes a lot of freekicks for a top team. I think he got probably two assists against Arsenal, but was actually mostly poor throughout the game, him, Hazard and Oscar gave the ball away constantly in that game, were rarely threatening in open play and two good dead ball deliveries isn't exactly a great performance.
Santi.... difficult to know, he's only had 2-3 really really good games for Arsenal, against Reading and Southampton, and he had 2 months being pretty ineffective inbetween which isn't exactly great. But he's in a new team and the rest of the team is struggling, at this stage impossible to know if its him, or the team, or both. Podolski/Santi look instantly hugely better when they aren't playing with Gervinho, or Santos, or Diaby, etc, etc.
Currently Mata>Silva>Santi.... Silva won't ever be better than Mata, too inconsistent and too crap against better opposition, Santi could end up anywhere in that list.
