First, the obvious reason... Because red is better than yellow in so many ways. Red shoes? Better! (Man with one red shoe as an example). Cherry better than lemon. Lasers? When do we ever see yellow lasers? Red light saber? Better!
I started out on a Rebel XS. I picked that over the equivalent Nikon because a good friend told me that I should pick what most people around me had. That way we could share lenses, accessories, etc. If more people around me had used Nikon, I probably would have gone that way instead.
What I've come to find, though, is that the used lens market for Canon is absolutely HUGE! More than half of my lens and body purchases have been purchased used. The prices are better, and if you don't find what you want, wait a day or two. It'll show up. Canon lens naming conventions are a lot clearer too. It is what it is, no extra stuff. I like that there are normally at least two lenses within a focal range. That way I can start out cheap(er) and work my way up if I know I'll use it more or have a specific need after using it for a while.
I'll definitely second the Ashton Kutcher comment. Don't really care for him, so would rather not employ him.
Deep down I think both are great. It's like buying tools. You can go to Sears and get Craftsman or Lowe's to get whatever they have. It's how the tool feels in your hand, and how it meets your specific needs. The only problem with this "set of tools" is that once you buy a lot of them, you are kind of locked in.
