Yui wins ugly, she's beyond hideous. They literally made her look like a biological man with that overextended jaw and her voice is just EUGH. Barf. Meg is pretty ugly too, prior to Yui she'd be my #1.
Prettiest probably goes to Kate. She's a cute country girl and has super cute and interchangeable cosmetics too. I think Jane is pretty too, she arguably has the best outfits in the game.