Please excuse my lack of knowledge as I've only used pockets and AIO. I'm just wondering why you would need/want anything other than a plain fitted if you have to put a cover on it anyway? Why do so many brands offer such cute prints etc., on their fitteds?
i asked this a while ago of one of the Qld ladies - to get the answer that, in the heat up there, often a fitted is enough as the kidlets run around in next to nothing.

won't be something i'll be getting down here though - i'll be needing a cover for sure!