Katy's having her moment right now, but just a few years ago Ashlee was on top.
NOTE: The question isn't who worked with better producers, but who is more genuinely talented?
Neither have incredible voices, both have been known to pen their own music a lot of the time.
Ashlee was never has theatrical as Katy is now but that's because Gaga wasn't around to re-introduce that to pop. ()
Ashlee by far. Katy has no talent outside of songwriting
Even Katy's songwriting is questionable. She writes with usually 2-4 other songwriters, meaning that it takes her and 2-4 others to come up with a lyric like "Do you ever feel like a plastic bag?"
Ashlee, since she did Dance School and stuff (read it off of Nirvana's signature). I think Katy is average songwriting, but nothing else is talented about her.