Why would I need to buy a nikon d7000 over a sony a57?

I'm trying to decide between two cameras and what I want to know is why would I need to buy the NIKON d7000 over the Sony a57? I'm not a pro, I just like to take really great shots in aperture priority mode.

You wouldn't. Just pick the one you like better.

You would probably pick the D7000 because its sensor performs better than the A57

http://www.dxomark.com/...ex.php/en… /Cameras/Compare-Camera-Sensors/Compare-cameras-side-by-side/(appareil1)/798%7C0/(brand)/Sony/(appareil2)/680%7C0/(brand2)/Nikon

And the D7000 is part of a professional system that has over 70 available new lenses and it can also use Nikkor legacy AF lenses.

I would certainly go with nikon d7000 it is much more proven SLR