Taking into account the fact that Bayern is far from what it was before, I would say that the chances are approximately equal. At least in London, Arsenal will be the favorite, and in Munich, Bayern. Historically, Bayern has priority, but as you know, it is not history that plays on the field, but the players. If we think strictly logically without paying attention to brands, then I would say that Arsenal looks like an easy choice to bet on, because this season they are more stable and have not had any obvious failures, while Bayern had all these problems and continues to have them.
It makes sense to consider where they are both worth estimating odds. In London, Arsenal has a chance of winning and in Germany, Bayern has a bigger chance for Bayern.
But more specifically, I am more partial to Bayern in choosing between the two to advance to the next round.
For the current journey of football, history is no longer a reference to ensure that one of the teams will go further because the players who compete are the determining factor.
Bayern is not doing well in the Bundesliga, while Arsenal is doing better. For me, when I compete in the Champions League, I will not judge that.
Bayern has more potential to qualify because of the x factor in the UCL.
The purpose of the x factor is that the experience and quality of the players in the Bayern squad are better than Arsenal's. Hopefully that's true.