I agree with Vinny but i think it's also hard to let your #1 overall pick walk away without compensation, which they would have done last year if they hadn't picked up his extension. I know they did the same thing this year, after paying him a lot more money but without a good look at the guy, I doubt Kubiak would be confident in saying "Yup. Get rid of him."
As for who they'd be better with? I don't know, but I'd say out of the three of them, Schaub most closely compares to Leinart. So Leinart.
New year, new attitude. Go Defense!