I'm not a Canon user, but from all the private instruction lessons I've given this year, I've run into both models, many owned by the same owner. In the end, for ease of use and based on the requirement that you only need 5-8 megapixels when it comes to getting your working published (line screen rule proves this for printing), then you're only wasting your money when you buy the more expensive one.
Again, I'm not Canon shooter, but I've had the ability to play with both models and work with clients that owned them both, we all
voted for the 5D hands down. Just my thoughts, wishing you the best, rg sends!
(April 2006 Playboy Playmate Holley Dorrough, now appearing at the upcoming Atlanta, Philly, San Antonio, Portland, Virgin Islands, Dallas and Chicago) workshops