According RetroRGB the difference between RGB and component is well-established and has nothing to do with bad component cables although this will exacerbate the issues. But is it noticeable? For the post part, probably not.
Regarding my convenience argument:
A component cable has separate video and audio leads and you need an RCA to mini-jack converter to connect the two audio leads to the OSSC. RGB on the other hand carries both video and audio in the same lead. Plus I’d like to use the OSSC’s component inputs for my Xbox and Wii.