I went to Yankee Stadium and Citi within a couple of days of each other. Yankees first. The atmosphere felt a bit flat. I wouldn't say it was a bad experience just felt nowhere near as good as at the Mets game. The crowd were not as involved in the game and I got the same sort of feeling that I get when visiting any massively successful team, a sense of entitlement to win.
And certainly around where I was sat there seemed to be a lot of "tourist" fans
Now i'm not saying a visit to Yankee stadium wouldn't be a great experience for a one off. It definitely would. Just as a visit to Old Trafford or The Allianz Arena would.