I have both the D5100 and D7000. Started with the D5100 but quickly found I was limited by the controls.
The D5100 took beautiful photos - see my gallery of the Wnter Jam concert. But when I wanted to get more creative, or push the camera, I found the controls somewhat lacking on D5100. The D7000 has flash commander mode, and the D5100 does not.
I use the D5100 as a back up and travel camera and the D7000 for assignments and serious work..
I prefer the light weight of the D5100 over the D7000, that' s one of the reasons I use it for travel and street photography.