Online Multiplayer GameCenter vs OpenFeint

I have real time multiplayer working in my game using Game Center, but I notice that OpenFeint also has an online multiplayer API. I know a lot of games support both GameCenter and OpenFeint for leaderboards and achievements but has anyone ever done multiplayer while supporting both? I’m wondering how it was done, as far as end users are concerned. When I click the multiplayer button does it ask which service to use, or what? Seems like it could get confusing for the app users.