When she isn't dressing like a homeless person, she's pretty much killing it! I adore Mary Kate Olsen for the casual (read hipster Brooklyn teenager) chic she exudes so effortlessly. 
The Olsens have impeccable taste, especially when it comes to picking the sort of simple and elegant basics that one builds an entire wardrobe around. And though it's clear that MK pushes the fashion envelope quite a bit, I much prefer Ashley with her more timeless approach to dressing. Which do you prefer more? :)