He tends to like what he knows. He grew up with a brittany and a corgi, and loves both of those breeds. It was easy to talk him into a Welshie because they're similar to britts.
Generally he likes medium sized athletic dogs who are pretty easy to care for and live with. He loves snuggly and tolerant dogs, as he likes to pick the dog up, swing it upside down, and do all sorts of weird things. lol He likes your typical lab personality, in a smaller body.
He has expressed interest in a GSD, which surprised me, since it doesn't follow his usual trend.