Which one should I buy? They're both about $200, both AF-S. I know there's tons of discussion on this, but a lot give advice like "try the kit lens at 35mm and 50mm and see which you prefer." The thing is, I'm buying this as a gift for my sister, who already has a D3100 and doesn't know what she wants. So: If you had to choose one, which would it be? (Yes, I've done me reading, and know how 35mm with the D3100's small sensor is more of a normal lens, but I've also read this, which recommends the 50mm anyway: http://prolost.com/1kphotos) Thanks!