One of them took Burnley to 19th place out of 20 in the premier league, and the other took Leverkusen to 52 win season, 51 in a row, with both Bundesliga title and domestic cup (and finals at Europa too).
So we can say which manager is better, even if somehow Bayern wins the title this year, we can be certain that you can switch the managers and Bayern would definitely win the title, right now there is still a chance that Leverkusen could win and all of that is only because of Xabi, if Xabi was at Bayern and Vincent was at Leverkusen, we would have seen Bayern win the league before week 30, and see Leverkusen be 8th. It was a horrible fumble on Bayern's part to get him, I do not trust what they saw in him at all.
I am a bit confused about this your comparison between this two managers. One thing is for sure, any manager that gets to coach Bayern Munich, their worst form as a manager cannot be seen because Bayern Munich squad is not one that can lose so many matches in a season irrespective of the person coaching them that season.
I won’t say it was a terrible choice for Bayern Munich to go for Kompany after the position he finished in the premier league and the team got relegated.
I understand there’s a connection between Pep Guardiola and Kompany who was his former player and also a connection between Pep Guardiola and Bayern Munich as a former manager of the team. Pep has this likeness for Kompany, he might have suggested him for them and for Pep to do that, then there’s more to expect from Kompany as the manager of Bayern Munich. I think he can do well and lead the team to success, this is not premier league but the Bundesliga where the competitiveness is less here when compared to that of the premier league.