For the hears Beyoncé's version is better, but she did oversing (like she used to in the past with some DC tracks) and she's not really connected to the song. Yes Vocally I still prefer Beyoncé than Britney, but Britney gives more emotions to it.
I voted Beyoncé because Vocal is ++ for me, And also she's my faves
PS: I don't know why this simple innocent thread turned into a big stan war mess...