Both could potentially turn into great players however the difference is you have to ask the question has Ross plateaued and if so why?
When Ross was at Davies' stage in his career he was doing what Tom is now. Was that just the enthusiasm of youth and lack of expectation?
In my opinion Ross could still be that player but he needs to address what goes on inbetween his ears. If ever a player was crying out for some kind of sports psychologist it's Ross. However Koeman strikes me as the kind of guy who would look upon that as mental weakness and deem him not good enough. I may be wrong.
I do think that Barkley has real problems with confidence.
This has culminated in him losing his identity as a player; as was rightly mentioned, he rarely drives from midfield beating players with his power and pace anymore.
He has been effected by having two contrasting managers, and this has messed with his head too.
I guess you have to question what we want from him.
I want him to drive, beat players, shoot more, look for forward passes, and press.
The trouble is, I'm not sure what Koeman instructs him to do (other than the preshing and forward pashes... sorry ☺️)