I am coming in a bit late and the purchase has likely been made, but I will respond for the sake of others that may come along....
Nikon vs. Canon is one of the most widely discussed topics in any photo forum. This discussion is also the most pointless discussions on any photo forums.
I agree with some things mentioned. For example, your choice of which brand to buy should include a consideration of the system. That includes lenses, strobes, accessories, etc.
I completely disagree with other comments. For example, To call the Nikon D40 a toy and then not say the same about a Rebel is funny. They are BOTH toys. Neither one of these bodies is going to be with you long. They are built for a market that will not be using it heavily. The bodies are built on very light frames. There is much more to a body than the sensor.
Canon and Nikon both make excellent equipment. They have similar lines in terms of camera builds. The both have low end consumer cameras, mid range advanced amateur bodies, basic pro (or high end amateur) and the high end pro bodies. The lens lines are also pretty much similar. They both have a range of lenses in good, better, best spaces. There is no lens Canon makes that Nikon does not have as well. This is true in primes and zooms.
What SHOULD make your descision as to what body to use it your personal taste. What "feels" right in your hand? What menu system is more intuative to you? etc. I would go and check the physical bodies. Hold them and see which one works best for you. Either brand is perfectly capable of excellent images.
DO NOT get caught up in what I call "tech hype" and "forum hype". By not getting caught up in "tech hype" I mean.... Don't get hung up on whether one brand is 12MP vs. 10MP. One shoots at 4.5 frames per second and the other shoots at 4 frames per second. Etc. By "internet hype" I mean that you should not get caught up in generalities and common myths that tend to evolve in forums. For example, brand x shoots with no noise while brand y is noisy. Brand x makes lousy lenses. etc.
If you want opinion, I am a Nikon shooter. I would not shift to Canon for anything. That's just my personal taste. It means absolutely nothing to a Canon shooter. I like the Nikon bodies for many reasons. One big one was mentioned. The Nikon F-Mount has not changed in 50 years. That means I can mount virtually any lens Nikon has ever made on my digital body. Right now, that may not mean anything to you starting out, but when you get into "your style" you might want to try some shots with a specific lens. I also love the ergonimics of the bodies. I've been shooting Nikon for nearly 20 years now.
Now, I would look into a slightly better body. Even if that means buying USED. Yes I said that. I would rather see you buy a used mid range body like a Nikon D200 (I am a Nikon Shooter) and get yourself some decent glass to start with. You can find a used D200 for about $650 on ebay all day. You will be FAR more satisfied with a mid range body. Particularly if you want to get into shooting models on a regular basis. Build up from there.
Hope this helps.....
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