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
I haven't checked the odds provided by the dealer at all. however, because this fight still has a time lag. changes can occur at any time depending on the situation. because after all, if one of the core players from the two teams is absent due to injury, the odds will automatically change.
but at least, we can see the picture that the bookies are giving for now. that Barcelona, is more favorite in terms of betting odds in the playoff match later. plus, Barcelona has the advantage of playing at home in the first leg. if Barcelona are able to overthrow Real Madrid in the supercopa cup, it is not impossible that United will be slaughtered by Barcelona at Camp Nou or it could be the other way around. At the very least, this fight will present a very interesting match and will present a very exciting battle, considering that these two teams have typical attacking formations.
Playing at home in the first leg I would consider a disadvantage in normal conditions but since the UEFA has made null that a goal in the adversary field were more valuable than when scoring at home,I can say now they have the advantage as both games are of equal importance and that Barcelona is in the best of their form after winning recently the Super Cup of Spain against their historic rival Real Madrid.
Manchester United on the other hand comes from one draw against a weaker team and a lost game against a strong team like Arsenal so the bookies are right to favor Barcelona to go further in this encounter.