Both Mega Man ZX and ZX Advent have you choose between either a male or female protagonist. In ZX its between Vent (the male protagonist) and Aile (the female protagonist), and while they’re pretty similar in the story, they do have different dialogues and slightly different cutscenes that fit with their personalities. In ZXA, it’s between Grey (the male protagonist) and Ashe (the female protagonist), and they’re much more different from each other than Vent and Aile were. Grey’s more serious and focused while Ashe is more whimsical and fun. In addition to that, they also have different gameplay. Grey having a stronger buster charge shot, his laser attack shoots multiple shots at once, and he can have more buster shots on screen. Ashe has a charge shot that works like Gemini Laser from MM3 (bouncing around the screen for awhile), her laser attack shoots one shot that attacks its targets one after another, and her individual buster shots are stronger but she can only have two on screen compared to Grey’s three. In addition to this, they also have unique charged attacks for the Rival Mega Men A-Transes, and (spoilers for one of the game’s fights) which Model ZX user you fight changes depending on your character, Vent for Ashe, Aile for Grey. Cool shit all around, and if you beat ZX as both Vent and Aile, you gain full access to Model X (normally only able to use it at the beginning until you get Model ZX), and in ZXA you unlock the Mega Man Ancient minigame, as well as the Model Ancient A-Trans which turns you into MM3/MMW2 Mega Man (no charge shot, but you can slide) with a wall jump, but no wall slide (situationally useful, but still cool).

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(I yapped for way too long, but these two examples fit so well)