Performance of any of the equally good players will be heavily affected by your formation and the formation of your opponent in each match. If you are, for example, playing 4-1-4-1 with 1 ST against 4-2(DMC)-1-2-1, I doubt the ST will score a lot but your wingers could and they will become MOMs...

My personal opinion is that the good player is the one that is great & stable on the season run and he does not need to have all 10s. If he gains skills from games as I would expect him to (being a fast trainer) and delivers an expected performance - he is a good player. Still, he will do it only if all other players are equally good