>>43953522The difference with Barry and Hau also ties to game structure. Palmer is the Tower Tycoon of the Battle Tower, which essentially makes him the boss of the Battle Frontier in Platinum and HGSS. In DP, Palmer uses Cynthia's battle theme, so you know he's a Champion-level opponent. His final team is all Legendary Pokémon.
Compare that to Hala. He's an Island Kahuna, an important role in Alola. He battles kids undergoing their island challenge. Nothing would make him happier than those kids growing and winning against him. He's a stepping stone. Yes, it's not his full strength, but as a Trainer, his goal is not to become the best. It's to raise the next generation.
Palmer isn't a stepping stone. He's not a Frontier Brain because he hopes you win and grow. He's a Frontier Brain because he became the best of the best in his pursuit of strength. He's not challenging the League, he's in a facility that brings in the most elite Trainers around. He doesn't mind losing because it means he can get better. Barry wants to be like him, while Hau wants to be like Hala.
The opening line to the Pokémon theme song captures that competitive feeling. "I want to be the very best, like no one ever was." That's the spirit of a good rivalry. It's the race to climb that ever-growing mountain.