Canon has a huge lead in market share. I MIGHT not consider the Nikon simply on the grounds of herd mentality

seeing the the INCREDIBLE difference in sales dominance Canon enjoies.
On the other hand if I were to start THINKING about the differences in detail... I would begin by referring you to DP review by Askey. They have very detailed reviews supported by lots of comparative images. And... I would add with saying the optical tecnology is more advanced with Canon versus Nikon... at least in their pro line. But if you are NOT going to buy pro line lenses then the differences are very very slight. This is more the case considering you're only using the sub-sized APS sized image sensor as opposed to a full frame sensor. With full framed sensors you need SHARP lenses for good performance in the corners...

and of course, the full framed sensors are going to yield state of the art sharpness and performance.

Which make optical deficiencies even more obvious IF your lenses fail at the edges.
As for how the DSLR performs... I feel the focus systems are more sophisticated and slightly faster with Canon.

And on the sensor and processing combination I would say the Canon images tend to come out flatter but as such they posses more shadow detail and smoother noiseless images. Nikon enthusiasts say they LIKE the contrasty default images that come from their cameras. That is nonsense as an original image that's overly contrasty is less likely to have shadow detail. I suspect only an ill informed enthusiast would prefer a universally contrasty digital original. Of course, I do not own a Nikon (although I used to be a Nikon SLR snob 2 decades ago)... so rather ... I do not own a Nikon DSLR. But I can say that externally I love the fit, feel, and quality of finish on the Nikons.
Another consideration... in the focusing systems. In matched model "side by side" comparisons I believe the Canons have more sophisticated and faster focusing systems. However, I do have a slight preference for the Nikon low light focus assist lamp versus the Canon srobing. However, that is a minor quibble as they both focus in fairly low light.
As for any other considerations. I think that some folks feel the Nikon interface is excessively sophisticated. This can be either an advantage or disadvantage depending on your POV. There are times when I might like the added features that are buried in the Nikon menus - and at other times I am comfortable saying the Canon is already more then what I need in capabilities. So- that may not be saying musch about MY creative skills.... today. For tomorrow I might advance into the exploring the few extra features in the matched level Nikon DSLRs.
Overall though - I have heard the images are far closer then dissimilar in purity. And you probably cannot go seriously wrong if you choose either a Nikon or similar Canon. Compared to all the Nikon bashing you've seen before this point you might wonder at my "about face". But only a fool would deny the advantages of having a weather sealed body on the mid range Nikon. I forgot which model it was but I was impressed that you could get that weather sealed feature on an affordable model... IMHO.
Cheers!
