Kara and Jay are tied in my mind. Jay's only faux pas was his first design, and Kara's bikini was also boring. Kara is professional, but Jay is the one with a raw vision which over time will become harnessed into something spectacular.
Austin, in my opinion, is farrr behind Jay. I liked his corn-dress, his wedding dress (which everyone else hated, I should point out), and his bathing suit. I was on the fence about his charmeuse dress and his future dress (it was nice but not future), and I really didn't like his Envy, his Costume, or his Postal thing. I dunno. He's definately better than Wendy though.