Depends on the gambling site. It's always worth checking a few to get the best ones.
For example, Duelbits tend to have higher rates for underdogs than any other sites. I've just checked and the odds for Barcelona Vs Bayern are as follows:
Barcelona: x2.05
Draw: x4.00
Bayern: x3.10
It's similar to rollbit that I use most times for certain games.
They have Barcelona at 2.07 odds and Bayern Munich at 3.15 odds. A little bit higher.
Bayern Munich at over 3 odds seems like a good option. Risk it all and make X3 of your stake. I think I'll try that even though I believe Barcelona will win the match. I'm not bothered about the odds for draw, because I don't believe the match will end in a draw, not like it's not possible, but I have considered it. I believe there will be a winner in that game.
How do you know Barcelona will win the match? Both teams ever got a lose in the last few matches. Barcelona got a defeat in La Liga match, meanwhile Bayern Munich got a defeat in UCL. Although Barcelona vs Bayern Munich is in UCL match, it is still difficult to predict because the performance of these teams are not 100% consistent. However, if we consider that the match will be held in Barcelona home, Barcelona should get the advantage. We can assume the chance of Barcelona to win the match is a bit higher.
Actually you have to be objective when talking about things like this. I know that Barcelona is not get a perfect team that can tear through anybody, it's still a work in progress, but if you look at the games they have lost, you'd understand that they were avoidable losses.
The loss against Monaco was due to a red card in the 10th minute. They played with 10 men for over 80 minutes and could have even drawn the game if they were clinical enough and if Flick made the right changes.
The loss against Osasuna was because of a heavy rotation that made him start the game without 5 of his starting players and mine you, that doesn't include the injured players.
Against Bayern, Barcelona will have Olmo back and fit and assuming no Barcelona player gets injured during the international break, they will have a very complete squad at home.
The only advantage Bayern Munich has against Barcelona is having more experienced players, other than that, Barcelona are superior going into this game.