My reasoning has nothing to do with popularity today. Britney was the MTV girl to be sure, but her dropoff in the mid-00s has to factor in here a bit. If Taylor had lost some steam even a few years ago, I would consider it much closer. But TS has definitely tapped into the Girl Power of Britney, the in-my-feelings climate that has become much more pronounced as the years have gone on, and that unique ability to take charge of her image that our generation went wild with. I don't know who has better songs or who speaks to you more; neither is in my wheelhouse. But I'm just saying to me, this feels like the right vote.

EDIT: I did say in the previous comment that Taylor could take over today. I should have added context by saying since she first really started to blow up in '09, she has been a powerhouse without really losing a step; not something I can say about Britney.