We still don't know exactly how much the odds, when look at stake, Barcelona have 1.75 while MU have 4.30 and the chance of draw is 4.30. Maybe this still temporary result until next month begins. But, we know in home, Barcelona is a club which is not easy to beat, MU performance is far away from expected, especially Antony which have a gap different like he played on Ajax
We probably won't see a big difference in the odds when the game starts playing, like you said Barcelona playing at home is a team that is not easy to beat and this gives them an advantage in this first leg, if United can make this first leg match draw then the opportunity will be theirs, but it will be a tough job in the match later