My vote to Skin Deep.
Mainly because Tallahassee’s two plots are quite disconected, like two different stories with the same character as protagonist. I mean, I know that the linking point is Emma’s distrust of Hook, which remains her Neal, but I can’t feel it as a unified tale: when FairytaleLand’s story got all my atention, then suddenly it changed to Emma’s past, and vice versa. It seems like the stories of the nightmares were closer each other than the main plots.
On the other side, you can feel Skin Deep as a single story, so to speak.
There is also another reason, more personal one. I know you are going to be totally shocked after read what i’m going to write, but i swear it is completely true: I discovered the Belle&Beast story after watching Skin Deep. You see, I’m sort of “disney virgin”, my fastination for fairy tales came to me being an adult and then I read the original tales from the folklore tradition, avoiding the romantic ones. BUT, I really enjoyed Skin Deep and it has made me become more open to certain stories. Not a very impartial reason to vote for it, but…