"Mr Mr" sounds better in full, the bridge redeems it.
I feel the whole electronic component of the song though is a lessor version of the electronics from "I Got a Boy", but I'm sure with some more plays I'll really like it.
Yoona is a filler end of. They can try to deny it, but she doesn't bring any flavor to the group.
I love the good sis but she is easily one of the weakest in terms of vocals, and she obviously isn't trying to improve. But I don't blame ha. She's still bringing in the $$$ just for existing so why fix something that isn't broken?
