I see a home game is Barcelona's only advantage. Their squad is not much better than their opponent's. But to call that if Bayern is being slightly favored in this game doesn't meet the reality. The latest odds still slightly favor them over Munich to win the game. And they probably get one or three points from Munich soon.
The trend and attention this match is carrying made me to have several toghts about the match despite the stats of Bayern been always the winning team against Barcelona in their last five matches that I have seen; it might end up been a game of how well experience your manager is which might favor Barcelona because Hensi Flick have more experience than Vincent Kompany. Barcelona might end up winning this match.
This is not the only effect. Both the technical director is more experienced and the match will be played in Spain. Considering these two authorities, I think Barcelona is the favorite in the match. However, we know that Bayern Munich is a strong team. The squad that Barcelona will announce before the match will be a factor that will affect the match in general. If important players are injured or cannot play due to a card suspension, Bayern Munich may be the favorite in the match.