We tried chatting with the Google+ Hangouts browser plugin, but at the time the performance didn't quite match Facetime on one-to-one chats when bandwidth was scarce.
My experience of hangouts is video is slightly jerkier (though in a controlled way if that makes sense - it felt like a deliberately lower frame rate rather than just breaking up), audio is more solid.
On a poor connection I'd go with hangouts over the alternatives at the moment. It's not perfect but I prefer the trade offs.
We tried chatting with the Google+ Hangouts browser plugin, but at the time the performance didn't quite match Facetime on one-to-one chats when bandwidth was scarce.