Ok, I have to admit something: I love this song and I have no idea what it's about. I've listened at least thirty times (today, sorry) and I still can't tell whether Britney is singing this from the point of view of two women into the same dude or whether she is trying to decide which is better: Fantasy or Curious. (Fantasy.)
This acoustic version doesn't make the song any less confusing, or the pronunciation of the word "baby" any less forced and creepy (actually all the words ending in y sound forced and creepy in this song, which is why I can't sing this song at karaoke or with other people present), but the removal of all the fun "pop" elements and the addition of Sia's vocals (Sia!) make this an excellent song to be wistful to or to put on as you dance slowly in the window, just one gentle tear rolling down your cheek. Just me? Okay!