I'm actually not sure any of his top three are great fits. If he comes here, he has to contend with, at minimum, Cassell, Samuel, and Adams for minutes. Even if he's the competitive type who doesn't mind competing for minutes, that has log jam written all over it - I think we're set at guard.
As
@tzznandrew points out, Ullis is a hell of a prospect and he's probably too undersized to declare early. There's no guarantee the Harrison kid leaves, either, and you never know who Calipari is going to sign during the spring period (possibly Newman). It might sound appealing now to join a program that demands exposure and play for a coach who knows how to get kids to the league, but by November of 2015, he'll be talking himself into playing 15 minutes a game as part of a "platoon system".
And St. Johns still employs Steve Lavin, who A) might not even be there by next season, and B) isn't that good at his profession. His best bet is probably UConn. Even if he has to wait his turn, he'll contribute right away if he can play and he'll be learning from the best. Doesn't seem like it's in the cards though.