I am not a Yankee fan. Why not? I don't know, I'm a good person?
There's no contest when it comes to the two teams or the two stadiums. Citi Field is just a fun time 'cause Mets fans are ridiculously more likable and human than Yankee fans. It's hard for me to generalize like this, but I've never met a Yankee fan that I didn't find obnoxious in some small way. I don't know what causes this anomaly. A guy asked me out once and I saw that he had a Yankee tattoo and that (among other reasons) was the clincher in turning him down. Is that modern prejudice? Or good sense? I don't know.
I've seen (not once, but twice) a Yankee fan SPIT on a player! (This is also the same reason I hate the Tampa Bay Devil Ray fans as well, those mutants spat on their own players! And yes, I know they're the Tampa Bay Rays now, but they'll always be the Devil Rays to me. Smug pricks.)
And the stadiums themselves? There are areas in Yankee stadium where you can't see the whole field! What the hell?! How is that a thing? Even the Yankee organization doesn't care about you! Nope, you can go right to hell. And in comparison, look how insanely pretty that view is from the cheap seats at Citi Field (above photo)!
If you're in town and you're deciding between the two stadiums, I hope you make the right choice. If you're sitting up high like I was above, there are a few wind tunnels that'll knock you on your ass, so be forewarned and maybe bring a coat. Will that kill you to bring a coat? Get over yourself.