Of those I would get the 450D. Reviews I have seen say that it's image quality and high-ISO performance compare to the considerably more expensive and much heavier 40D; and it comes with the new (and much improved) 18-55 IS kit lens which the 400D doesn't..
There is no comparison the 450d is runs rings around the 400d...
The 450D is a better camera than the 400D but really not by that much; if you have the bucks, better off with the most contemporary camera as it will fade in favour over the years as the new sexier models come out. If you don't have the bucks, then get the 400D, you still can take award winning photos with it.Maybe the writing on the wall could use a little revisionShane Koyczan (Slam Poet)http://www.youtube.com/watch?v=f02Q5IFoyKw&NR=1..
Generalities and exaggerations that are not really very helpful..
Doesn't make much difference. You'll get prints that look the same..
The big advantage of the XSi is that it comes with a better kit lens, incljuding improved sharpness plus "free" image stabilization..
When in doubt,newer is better if your budget permits..
I know you said you couldn't afford it, but the choice for me would still be the Canon 40D. They've recently lowered the price to the point that for around $900 you can pick up the 40D body..
The XSi is around $900 with the kit lens. To me, the 40D is just a much better camera and worth the very small difference if you can somehow afford it. The difference is the cost of a lens..
Just my 2cents.Cheers, Craig..