Noise makes a difference to me much of the time but not always. The overall quality, including the crispness/sharpness (not referring to focus here) can be very dependent on the level of noise-less-ness of the camera’s sensor, most often visible of course in low-light situations. When shooting indoors, at weddings, or portraits in darker/shaded areas or at dusk, I would never want to use my older Rebel because of this. It’s not that I’m going to necessarily print every photo, but having the option to do so, and giving my clients the option to do so (in large sizes) to me, is part of the professional aspect. Given good lighting conditions, a low-end or older body with a sensor that produces more noise is still going to produce a good photo and be relatively noise-free. Because I’m not always shooting in perfect lighting conditions, I use a camera that can handle low light well- the 5D Mark III.