Good point to make. If you have AW Sherry and Olivie, then Yuyu may outclass Belinda in performance (since if both are deployed Yuyu is getting buff too) since Belinda gets neither buff. Buffs like Uzume, Aria and Prince don't count since both get those.
Side Note: My Yuyu min-costed ages ago, so I tend to forget her original cost is 14 (13 after AW), because mine is at 10 lol.