Its so hard to decide when they're both hot in such different aspects. Like Scarlett comes off as like a classic sex fantasy kind of hot... but Emma is just so beautiful with a great personality... she's kind of like the dream girlfriend you always wish you could meet.
I know that Scarlet may be "sexier" in the traditional sense, having a larger bust, and a more curvaceous figure. But I vote Emma. She just seems so elegant and classy. She isn't like a lot of young actors nowadays who spend more time on the tabloid pages than on screen. She knows how to present herself in a good light, she's charming, dignified and...I dunno, just unique. To me, Scarlet is just another hot girl, but Emma Watson is perfection.