Bayern Munich also lost when they faced Aston Villa so the strength of the two teams is not that different in my opinion. Barcelona's chances of winning are much greater even though Bayern Munich are in much better overall condition.
Honestly, the strength of Aston Villa and Young Boys cannot be compared. Aston Villa is clearly stronger this season and Bayern Munich lost when facing them while Barcelona won big when facing Young Boys but lost when facing the league 1 team Monaco. In my opinion, the strength of Barcelona and Bayern is not equal. I think Bayern is still quite superior in the UCL at this time. I think Bayern Munich will probably beat Barca's troops later.