Castles big and small...it's all about the sight lines and space the designers have to work with. Magic Kingdom and Tokyo Disneyland have giant, expansive spaces to take advantage of with little or nothing surrounding it that would be bothered (yes, bothered) by the sight of a giant fairy tale castle looming in the distance.
Disneyland and Hong Kong Disneyland don't have that luxury.
As for the painted look to each Cinderella Castle, I don't worry about it that much. As long as neither one looks gawdy, it's not really worth wondering about IMO.
-- PMM