Right let's analyse the four penalty incidents.
1st one on Oscar: a slight clip on the heels with very little contact. Would have been soft to give that. Oscar could have done more to stay on his feet, in my opinion.
Cazorla on Fabregas: anyone who thinks that is a penalty is a pussy. Was there contact? Yes, very minimal. Just because there is contact does not mean it is a penalty though. There certainly was not enough to bring him down and he was looking for it. Rightfully booked for simulation.
2nd one on Oscar: clear penalty, in my opinion. Ospina wiped him out. Amazed the referee didn't give it, however it can be argued that he played advantage but Bellerin cleared it off the line. As has been mentioned before, the referee are privy to certain rules that we aren't, so it could come down to the interpretation of their rules.
Cahill handball: again, I think this could have gone either way. On one hand, Cahill was on the floor and was like a yard or two away from the shot. On the other hand, his hands were raised and it depends what the referee interprets as an "unnatrual position". Equally just because there may not be intent, does that mean it isn't a penalty? Not sure myself.
So out of all the 4 penalties, there was 1 which was clear cut and the rest consist of a dive and 50/50s. How is this any different from most matches in the PL?
Even if the penalty was given, there's no guarantee they would have scored it.
And looking aside from the penalty incidents, on the balance of play, I don't think you can really argue with the result.