I think all the mid level canon-nikons are close enough you'll be happy either way. They both do more than most of us will ever use and are great investments. I've had canons over the years and I guess it's a little like Ford/Chevy where I have a perceived preference. Like plowboy said, invest in lenses. I have 5 ranging from micro to 300mm telephoto that I can shoot just about anything with them but we keep a 50-100 on it 90% of the time. Do it, you'll be amazed at the difference it makes. You'll end up driving/walking around looking for things to shoot.
Mike