i'm in your conscience
I've always liked Wattson. I know that's a weird answer, but I always found him to be a pretty cool guy. Plus you get Thunderbolt from him for doing a nice little sidequest, and I like more chances to level up tbh. And there's a Thunder Stone in that area. So yeah. Even though RSE are my favorites, I've always found that the gym leaders of that region really lacked in personality, aside from Wattson and Wallace. That's just game wise though. I'm sure they were better in the anime or something.