All else being equal, especially including the final print size (a factor which often gets ignored and confused with respect to pixel peeping), the larger the format, the better the image quality in every aspect. That includes sharpness as well as noise / grain as well as dynamic range as well as anything else you care to mention.
Of course, all else is never actually equal, which is why it's important to compare complete systems. Neoruanatomist made that point; better theoretical maximum image quality is useless if you can't properly operate (in the specific case, focus) the equipment.
There's another factor to consider. Image quality with even entry-level DSLRs and kit lenses is superlative. Anything going to the Web, 4x6 prints, and even 8x10 prints...there's no practical real-world image quality difference between a Rebel and medium format (with the exception that you can more easily get a greater amount of background separation with the larger format).
Once you're printing on a machine that won't sit on your desktop, though, the difference between the different formats starts to become apparent. You can make a great roadside billboard with a Rebel and a kit lens, but walk up to a pair of door-sized fine art prints, one made with said Rebel and the other with an 8x10 view camera, and even your half-blind great uncle will be able to tell the difference.