In my opinion I prefer Manchester United ahead of Barcelona. Because Manchester United team players are more experienced than Barcelona team players. If these two teams go head-to-head, I think Manchester United will win by a landslide.
I think that you shall watch the history of head to head between barcelona against MU yet MU has more chance caused by xavi was the worst coach for barcelona. Mu may on advantage over barcelona. Barcelona is quite strong at this moment with lewandowski who has become pure striker for barcelona. We will not know the winner if we will not watch the match between barcelona against MU which will come next year. Lewandowski may help barcelona to beat MU but i hope that MU will become a winner.
MU can beat barcelona in the current form.