Blue Jays as I grew up believing that Canadians should stick together and cheer on one another. Watching the Blue Jays win back-to-back World Series' in 1992 and 1993 were some of my biggest sporting highlights of my life. To be honest, knowing what I know now, I probably would have chosen to cheer on the Mariners if I was starting off as an MLB fan now but it's impossible for me to do that now. Too many childhood nostalgic memories with the Jays. Guys like Carter, Alomar, Devon White, etc., are almost as dear to me as Linden, Bure, McLean, etc.
p.s.___________One thing I'll say - after having lived in Toronto from 2013-2015, I can honestly say that if the situations were reversed (i.e. Vancouver and Buffalo had MLB teams instead of Toronto and Seattle), 90% of baseball fans in Toronto would cheer Buffalo over us.
After the 2011 Cup loss and seeing how most of Canada cheered on the Bruins over us, if I had the opportunity to renounce my Canadian citizenship and become a "citizen of the Pacific Northwest," (if there was such a thing), I would strongly consider it.