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.
The component argument needs more data. The only place on retrorgb.com that mentions any issue with PS2 component output is a single sentence that stating “[t]he component video encoder in the Playstation 2 is known to be a bit noisy.”, with no data or sources to back up that claim.
I believe (and I could be wrong) the last thing I heard from Bob from RetroRGB regarding this issue was something in one of his Retro Roundup videos that there was a question of quality of the component cables being used, and that further testing is needed, but that was sometime back in 2018, and nothing has been mentioned since.
Also regarding your convenience argument, I’ll agree that having the single SCART connector for everything is more convenient, especially if you’re continually swapping cables (except regarding the SCART port on the BeharBros Toro; that thing flexes way too much). You could, however, very easily get an automatic component switcher, hook up all three consoles, and then you’re not continually handling that part of your setup.
Even if you don’t want to have all of your consoles hooked up and available 24/7, you could just leave the OSSC, switcher, and AV (and optionally power) cables hooked up, and then you’ll only need to connect the AV and power cables to a given console when you want to play.