I would choose Brown regardless of water polo.
I had one kid at Harvard and one at Brown and much preferred Brown.
Recruiting was very strong by the way, and what we call the Brown mafia continues to network and share opportunities.
And if Brown doesn’t accept him, he can apply to Yale RD.
Brown admissions is quirky. I know people who got into Harvard and Yale but not Brown. It seems he has a good chance so I guess the problem in these posts, for you, is that if he gets into Brown then he can’t go to Yale.