Attractiveness (is that a word?) Is not just about who is more cute than somepony else. I offer that when taking whole-pony approach you will find Rarity is the more attractive pony.
If personality is attractive than rarity wins on that alone.
What about dedication? Rarity again.
and each of TEOH? Rarity wins on each of them.
I could go on and on here but to save your eyes for cooler posts I'll keep it short,
Rarity is most attractive pony when you think about the whole pony.