Raph was the pro pick in Turtles in Time, and I think the differences between them were the same in Hyperstone Heist so there too. He had the worst defense, but if you're getting hit you're not pro. His speed was the best, and his dash attacks were GDLK. His special move was also the strongest, but I don't usually use those.
Don was Simple Mode in those games. His reach kept you safe, and even if you did get hit he had the best defense. But you couldn't feel good about yourself winning with him.
Leo was basically unplayable due to the fourth hit of his combo having absurd recovery due to making you hop. You would get hit before you landed 9 times out of 10.
Mike has the strongest normals and good everything else, and is, IMO, the pro player 2 pick.
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SuperNiceDog didn't have to reconcile his name...
But Dauntless Hunter is now MrGreenonion