Pros and cons on both sides.
I had a look a little while back and thought that Nikon was ahead on the bodies but Canon had the edge on range of lenses available at good prices.
However, Tamron and Sigma both do lenses for Nikon and Canon with specific mounts for Canon and Nikon bodies, so if you don't mind going down the non-OEM route for lenses, then that's a good option.
If you still have your old lenses with FD mount, you can get an adaptor to use them on the newer Canon bodies.
Main thing is to go into a shop and try them out. Last year, I went into Jessops to try out a Canon 400D but found that I didn't like the feel - too small and I missed the control wheel my film EOS 5 had on the back. Went up a couple of hundred quid and bought a 40D instead. It's a more rugged body, fits my hands better, etc.
Moral of that story? Spend half an hour in a shop trying stuff out even if you're buying off the interweb.