the 5100 is a much newer model. The sensor, autofocus, metering, etc.. are all improved on the 5100. Seeing that you are getting a new camers, I would recommend you get the latest one, and the 5100 is not an expensive camera.

I think they are being sold with 18-55mm lens as a package. If you can afford to get the 55-300 or 70-300 lens then you will have a good staring kit.