Indeed, Leipzig is more promising than Frankfurt in terms of performance and this can be a pretty good reference for those who want to place bets on the DFB Cup final. Maybe Frankfurt was lucky enough to beat Freiburg in the last weekend of the bundesliga yesterday, but that still hasn't proven its capacity to beat Leipzig.

Especially if we look at the odds offered by the bookie, it's quite clear that Leipzig is favored to win with odds @1.73 and for Frankfurt to get odds @4.30, it's clear that the difference is very big, so I don't think there's anything wrong with betting on a team that will clearly win the DFB Cups this season.
The odds are still interesting because this is not a home game for Leipzig, but it takes place on neutral grounds. Frankfurt has an amazing supporter crowd and I am sure that these fans do everything they can to get into the stadium and support Frankfurt. I believe that Frankfurt will have more support in the Berlin Olympic stadium than Leipzig. That can definitely help a lot when the game is close and not decided after half an hour because Leipzig scores early goals.