Disagreed. Salty has graduated from prospect status, but in BA's 2007 list he was #56, above the likes of Pedroia, Joba, Carlos Gomez, Kurt Suzuki, etc. Kottaras, this year, in about the same level as Saltalamacchia was then, is #20 in SoxProspects.com's list. Salty already has 500+ MLB at bats, and while not the greatest of stats, does have experience, something that Kottaras cannot claim.
Actually I would say Brown will be a AAAA player. He's 26 and hasn't been called up, and while he is a very good defensive catcher, has a ceiling of a backup catcher. Kottaras has a higher ceiling, but it remains to be seen what he can actually do.