I disagree with what most people are saying here. I'd go with Leiter over Millwood in a heartbeat. Better ERA, WHIP, and probably wins too (marlins are going to be very good this year).
Also, Millwood gave up a HUGE amount of home runs last year, which is usually a very bad sign of things to come - plus, he had alot of run support in his starts so HE got lucky in that regard.
Also, to whomever said that a change of leagues is always good for a pitcher - you're wrong. Especially if that change is from NL to AL, where the hitters are much better.