The first one definitely. The 3rd and 4th have home-type roofs, like, pointy, and that would make it look like a regular house ghetto rigged as a gym. So, the flat roof looks better, because theres no upstairs. Also, the second one doesn't have a pokéball sign, which looks unprofessional on a Pokémon game's stand point.
Anyway, looking good, good luck!