I haven't played this game. Waiting for English version to be released soon.
But looks like I vote Cheren as my favorite B2W2 Gym leaders. Now he is more cool and handsome. I love him! (I'm not a gay person -"-) Following number 2 is Clay, Roxie, Elesa........ and the last is Marlon. Maron isn't that too bad. I like him as well as I love all Pokèmon Company have created.