>>56359378May is very different, she's far less confident when she speaks and occasionally stutters, she's more prone to being flustered, particularly near the beginning. Brendan isn't a huge asshole, but it's all the subtle things. He seems to be disappointed that you're a girl because he assumed his neighbor would be a boy since he heard your father was a Gym Leader. He's not outright rude, but he doesn't speak to you with any respect and you get the sense that his pride is hurt because he views himself as being above you. He's not to the extreme of the Gen I rival who will sometimes refer to himself as "Ore-sama" and regularly boasts and never seems to acknowledge your victories outside of his losing dialogue and the post-final battle dialogue.
ORAS does change or add a solid amount of dialogue, there are a number of lines where Brendan will use ageru.
I got Red and Leaf's dialogue from their interaction with Copycat and Red's observations of the TV in his house and the Super Famicom in Celadon Department Store. Copycat is the only time where Leaf uses "you" (anata), but Masters must have forgot so they write her as saying kimi.
Kris, Elio, Selene, Chase, Elaine, Victor, and Gloria never appear as NPCs or have internal dialogue in their games, so I only referenced Masters.