The easiest of arguments.
Is a squad player staring at the 5th best team in the EPL better than (possibly) the best midfielder in the Championship?
Having seem both play I believe they're of similar stature to each other along with Stuart Armstrong ( who plays at a better level than John McGinn- but this doesn't matter). Callum MacGregor is more talented than Scott, John, or Stuart but he doesn't play in the EPL but that's not important, because what makes a good player is their ability to play not their club.