The Schoolgirl RBD dolls are on the shortened "Hobbit" body while the Concert RBD dolls are on normal-Barbie bodies. Yay Concert dolls!
However, the hair styles on the Roberta Schoolgirl and the Roberta Concert dolls differ. I think the Schoolgirl doll has a prettier face - she has a right side part. The Concert doll has short bangs. Guess who's going to play Frankenstein and swap heads? Ah, you know me well LOL.
Here are the photos for comparison:
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