Walrus Close-Up at SeaWorld Orlando is one of my favorites, getting to meet Slowpoke the walrus, interacting, and feeding.
I have done Beluga a few times at Orlando and other parks. It is hit or miss, sometimes a great experience and sometimes so-so. At Orlando, it really depends if it is BTS or on exhibit. If BTS, you get to interact with and have hands on with the belugas. On exhibit was a disappointment, just tossed some fish to the beluga and minimal behaviors.