Canon's camera system seems to change more often than people have hot dinners. Maybe it's not quite as fast as Pentax's changes where a camera might be a XX1 one week then because it has a red dot on it, an XX2 the next week then an XX3 the following when the dot becomes a square.
Canon seems to have an 18 month lifecycle for each model of camera with 12 months between introductions of new models. Each new model has some quite inconsequential changes over the previous model. Canon probably catches the "keeping up with the Joneses" market by doing this but the reality is that there has really been no really worthwhile change in digital cameras since 6 megapixel digital SLRs came out.
6 megapixels (or 3 if you frame accurately) is more than sufficient for most people. Most will never print to greater than 10 x 8 which a 3 megapixel camera will do perfectly well. There are a few die hards who will want to print to the largest possible size that they can, believing they are professionals when in fact they are the worst kind of amateur; the kind that knows-it-all and has to have the best equipment yet never ever seems to display a recent photograph. Indeed, Feininger mentioned this in his 1970s book "The Complete Photographer".
People have been suckered by Canon into buying new camera after new camera as each new camera is introduced with huge razmataz. The truth is that a 5D III will take a picture that looks just like the picture my 8 megapixel XT will take. There is no tangible difference. I'll repeat that - there is no tangible difference in image quality. Sure - the image might be bigger but that's very much a moot point since digital images are very rarely printed and even more rarely printed to greater than 10x8. In fact, the biggest centerfold in a magazine being Playboy's centerfold is 10.5 inches by 30 inches. At 100dpi (which is about the highest quality a magazine will ever achieve), this is 1050 x 3000 pixels. A standard Canon XT is 2304 x 3456 pixels. That's more than adequate for a magazine and even for a centerfold - not that anybody is really going to be out there shooting Playboy centerfolds other than Playboy staff (who probably use a medium format camera instead of one of the miniature formats).
For the average Joe, there's precious little difference now between any of the Canon cameras other than price. The video feature and live preview are pretty much gimmicks. Canon keeps churning out cameras with minor differences and new model numbers and people keep falling for the oldest trick in the book.
The Canon camera system is a series of minutely different cameras with differences that don't mean much in the overall scheme of things. 99.99% of Canon camera users are never going to print to more than they can print with their home inkjet which will be 8.5x11. Believing they will is delusional thinking. Ages ago, I bought a printer capable of printing to 13 x 19 and have never printed to more than 8.5x11. That was originally purchased when I had ideas of printing larger photos to sell through a coffee shop. The coffee shop went bust before I printed anything.
Users will cry there is a vast difference between models yet in reality there isn't. At the end of the day, the most important thing is correct editing. With poor editing a brilliant photo taken on a top of the range camera will look worse than a casual photo taken with a cellphone. Most users aren't capable of great photography nor of great editing. Their foolish belief is that a better camera will make their images better. No - it won't. A poor camera in the hands of an expert will produce images that shine amidst the mediocre attempts of most amateurs.
The difference between the top and the lowliest models of Canon camera are nil in terms of image quality. The handling will be different but not so much that the average amateur will really notice and the true professional will work around the flaws of whatever camera is in use. So - to all practical purposes - there's precious little to choose from bar price. The cameras are all the same.
The biggest problem with Canon's cameras and this goes for all digital cameras is that the manufacturers have totally forgotten what a camera is for. They're loaded down with gimmicks that are pretty worthless. Scene modes and minuscule settings adjustments when all people really want is four modes - aperture priority, manual, shutter priority and program (with program shift). The fancy extras just clutter up the controls and make the camera fiendishly difficult to use. Who on earth carries their camera manual with them all the time? Time for Canon to rethink what they're doing in the camera business.