I have the Canon 24 Tilt shift bought new about 5 years ago and the Nikon 24 PC bought new about 11 years ago. Both are in like new condition. I did some testing this past year to see if there were any differences between the two. I tested them indoors in a well sunlit, south facing, two story ceiling, living room with a lot of windows. From the few shots I did where the camera was on a tripod and only switched out the lenses, I found my copies to be identical in sharpness, contrast, color rendition and CA. I couldn't pick one over the other. Each lens was shifted to its maximum where they both look pretty bad. With that said I still only use the Canon for my work. Occasionally I have need for the tilt but mostly would like to weld it in place. If you get the Canon beware of the tilt! It is very easy to have the lens with some tilt dialed in if your not paying close attention. I check it with every shot. A royal PIA.
Peter