Started as a Sabres fan, too young to remember ever making the decision in the mid-70's. Anyway, my favorite player was Barrasso. He got dealt to Pittsburgh so I started to cheer/follow them. This was the late 80's with Coffey, Lemieux, Barrasso, et al. The Cup years happened and Pittsburgh had added Jagr and really usurped Buffalo (who were constantly trading away guys I liked-Barrasso, Housley, Turgeon, Mogilny) for me.
Currently, Pittsburgh is #1 with Buffalo #1b. They've only met once in the playoffs (2001) and I really didn't enjoy the series. I thought Buffalo would have a better chance against Jersey but the Pens won and lost to the Devils in five. Even when the Sabres were really good 2006-2007 I still pulled more for Pittsburgh.
Normally, I would make fun of guys with two favorite teams, but until you've been there...
My Best-Carey