Specs only tell half the story, the resolution difference is massive, so is the fact that the iPad 3 has a *10 hour* battery life.
Doesn't really matter either way though, we know the iPad 3 will crush the PSVita in sales.
The "20-something" demographic Sony is trying to woo (and was abandoned by on the PSP) with the Vita is fine playing iPad/iOS games on the go in between checking emails/Facebook/Youtube/Twitter/etc. etc. etc... fact is after you get out of your teens, most people between school/job/family don't have the time to play a handheld for hours and hours on top of the console they have sitting at home (with 50 inch screen). Priorities and all that, y'know.
Nintendo has a lock on the kids/young teenager handheld market. Apple is the "cool, hip" lifestyle company that older teens and 20-30 year olds flock to. Which leaves Sony stuck in the middle of nowhere IMO.