Arsenal aren't the same as their 2017 version anymore. They are much more competitive thanks to Arteta's management style. You should be remembering their last draw against Bayern Munich. How it started and how it ended... It wasn't different than seeing a nightmare truthfully. However I'm not expecting a similar result this year.
The reason is not only the improvement of Arsenal team. It is because of Bayern Munich's being likely to be quite unreliable with their game this season.
If you ask which one of these teams would qualify for the semi finals I would pick Bayern Munich though. It is especially due to what I saw in the Arsenal - Porto draw.
Arsenal is a team that is quite consistent this season, it is not easy to be in the top 3 of the EPL, especially since their opponents are Liverpool and Man City, while Bayern is entering a phase that is not very stable, they were only able to end in a draw with Liverpool, when the match was between Arsenal vs Bayern wins, then it is very likely that the final result will be a draw, Bayern has Harry Kane, who is quite capable of breaking through Arsenal's goal.The reason is not only the improvement of Arsenal team. It is because of Bayern Munich's being likely to be quite unreliable with their game this season.
If you ask which one of these teams would qualify for the semi finals I would pick Bayern Munich though. It is especially due to what I saw in the Arsenal - Porto draw.