Your best is the little guy. Just have to nanana-booboo for a sec.
I have two 98% snorlax's. One with hp/atk best with lick/beam. The other hp/def best with zen headbutt/body slam.
Point is, those came after I already had one strong IV range Snorlax up over 3k. And I never looked back. It sucks, but it's the same thing with you. Just start up the good one.
Also, body slam is legacy, I believe, so you will NEVER get a better gym defender then that guy anyways.