Due to all the reasons that's been stated so far, I have to go with Starmie. ^^" Starmie does not have the highest Special Attack stat, but it does have decent Speed. Thanks to that, it will always be the first to attack. Plus, it could use Rapid Spin, which could clear your field from entry hazards and allow you to switch between Pokémon as much as you like. Wailord may be bigger in size, but Starmie is simply better.