Generally its the lenses that drive the choice. Canons lenses are better but the current Nikon bodies are beating the Canons.
After having the 18mp sensor in the 7D I wasnt overly impressed with it. There is a slightly updated one in the 650D. But its an old sensor and its performance shows that. But then im very anal about the image quality. For the average user printing up to A4 the quality wont be distinguishable. Also depends what lenses you are marrying with the body. All these new high MP sensors need good glass to resolve the IQ and the standard lenses don't offer that quality so results aren't as good as they could be.
Put it this way putting a poor lens on a high MP camera is like putting plastic wheels on the Z4. Great car but ruined because of the tyres lol.
The Canons are much better for someone leaning tho, the controls are much less complex and menu systems easier to navigate. The Canon system is a winner over the Nikon in my mind, but the Nikons with the new sony sensors are slightly better at the moment. But the rate they bring out cameras that could switch at any time. Canon are about to announce their new sensor tech with the 70D/7DMKII which will come down into the XXXD line. So I would wait if you like the Canon camp.
All the cameras you are looking at are awesome, but I would put an air of caution on the MP count higher is not always better, higher pixel density means more noise. Also the 7D and D7000 are more advanced cameras, bigger and heavier.
What I would do is go have a look at them and handle them. See which you like best. They are so similar its completely down to preference.
Might be worth looking at the mirrorless market. Small compact size cameras with DSLR sensor quality.
I took a few with the 7D which is the same sensor as the 650D
BMW i8 BMW iPark Lane by
TomScottPhotographyCumbria, on Flickr
BMW i8 BMW iPark Lane by
TomScottPhotographyCumbria, on Flickr
These are at 1000ISO
IMG_8341 by
TomScottPhotographyCumbria, on Flickr
IMG_8427 by
TomScottPhotographyCumbria, on Flickr
But most of my favourite pics were taken with an old 40D so...
BMW E92 M3, Rig shot by
TomScottPhotographyCumbria, on Flickr