As a longtime photo enthusiast (and technically, as I recently sold a photograph that was used for the album cover for a friend's recent album, a professional) who has followed the product lines of both Canon and Nikon over the last 10-15 years, I'd say the answer is... "either". On a number of occasions, Canon has come out with a new technology or breakthrough in price or function FIRST, but Nikon would follow up 6-10 months later with a better implementation. My perspective is, you can't go 'wrong' with either one and many of the differences at this point come down to approaches to ergonomics and or personal preferences for controls and layout of the camera.
I have used Canons since the mid-1980's when my photography hobby became serious. I use Canons now, not because of a specific difference in my view of Canons vs. Nikons, but rather because of my investment in Canon lenses would be difficult to replace if I were to jump ship to Nikon or another brand of DSLR.
I currently have two Canons, my primary is the Canon 5d Mark II, which has, to an old hand like me, unbelievable low-light performance, and my secondary is a Canon 40d. I also have a small Canon s570is point and shoot that I keep handy just in case when I am not carrying my camera bag around with me.
Here's one of my first shots I took with the 5d Mk II. It was in a dark club, handheld in extremely low light.
http://www.chefjuke.com/GALLERY/PHOTOS/slides/IMG_0184.html
In my film days, to take a shot like this, I believe I would have ended up with grain the size of pingpong balls.
Thanks for your excellent comments. I am leaning towards the Canon 5D Mk ll as well