I would suggest you to go for Canon because Canon has a better line up of Lenses with varieties suitable for occassions and type of photography. I am currently using a Canon EOS 5D and it is awesome. Previously I was using Canon EOS 300D, then Canon EOS 30D and now Canon EOS 5D.
Nikon lenses are very expensive compared to an equivalent Canon Lens.
Please go for Canon EOS 450D(Also known as Rebel XSi)with EF-S 17-85mm with Image stabilizer.