Tough choice, but I'd deal whatever one has more trade value -- which will vary one owner to another.
I'd keep Cantu and deal Weeks (because IMO he's got more trade value).
1.Roger>Randy this year; 2.New Yankee SP's = BUST! (again); 3. Bernie will cover the least amount of ground of any CF in baseball for 4th straight yr.; 4. Yanks = stuck with Giambi's contract; 5. Loaiza > any SP signed in offseason by Yankees.
the are both good options at a shallow position, i think they are about as even as it gets. in the future i think that weeks will be better, but for now i would take whichever 1 u could get for cheaper