Well I'll start by saying both cameras are excellent & most photographers will find both cameras can more than meet their needs for the years ahead.
I believe it comes down more to personal taste & how the camera feels in your hand. I was considering various Canon models vs Nikon last year & on holding the various cameras I came to the decision the D200 felt right for me...... so I bought that model.
The big expense is going to come with your lenses & once again both make excellent lenses, in addition to the likes of Sigma, Tamron etc. Here though I personally believe you get more for your money with Canon lenses, with some of the "L" lenses offering great value for money. In addition there is a bigger second hand market for Canon, so you have more choice.
So in summary ,down to personal taste
