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.
I think in this case we cannot ignore history in a competition between two teams, because after all we often see a strong team that is difficult win when to meet another weaker team because they have a bad history with that the weak team, however the history of statistics and head to head of both teams sometimes becomes a moral support for a club and will certainly make the motivation of the club's players stronger to be able to Making history is maintained, and that's why I think Arsenal will be inseparable from their dark story when they meet Munich in the Champions League.
So far we know that Arsenal always have nightmares when meeting Bayern and this season Arsenal also inevitably must meet Bayern again, to be honest I personally am a little worried about Arsenal's chances of going far in the Champions League this season, although Arsenal is now starting to look as a strong team in the league but for the Champions League it seems they have no change at all like the previous season, Especially when we see if they are very difficult in beating Porto in the first and second legs of the round of 16, while Munich who are down in the league of course they have a stronger mentality when playing in the Champions League and that's why I say if it might be difficult for Arsenal to beat Bayern Munich, especially in the second leg later.
I personally would love to see Arsenal go far in the Champions League this season but am a bit pessimistic if Munich are their opponents.