Peach is not short and has joined Mario in the fray. She is in smash bros and she is not helpless. I think that is what this question is asking not which girl you should date. Mario beats sonic so peach would beat Amy as well. Even peach can beat sonic.
She is not helpless. She can cook, Clean, And wield a hammer like a boss. Peach is always getting kidnapped and makes Mario risk his life to save her. Then she teases and messes with his heart.
Mario wanted to marry peach because he genuinely loved her and his love motivated him to defy the odds and she brushed him off.
Mario should not waste not his time with a cold heartless she beast that toys with him. He should just leave peach alone and let her fall without him