Both are very good camera, the best thing for you to do before starting to invest in a company or the other. Go in a store and get a feel for both camera.
It would be a waste of money to get a lower end camera only later to want to upgrade. I done that and now I have the D3100 laying around because I should've gotten the D7000 at first. Getting a D7000 or 7D might look intimidating at first but you will learn to love them.