The first thing I always judge a footballer by is his first touch. The ability to control a ball quickly, to remain in close control of the ball and then find a team-mate with accuracy and correct weight of pass.
But that's too simplistic a definition. Sometimes it's not about keeping your first touch in close control, sometimes it's about letting your first touch put the ball ahead of you to run onto, or away from the pressuring opponent. Passing isn't just about weight and accuracy, it's can be about being on the same wavelength as your opponent. A perfectly weighted, accurate pass can appear to be errant if the team mate your passing to suddenly stops and changes his mind about where he is going to run to, and that can't be put on one player, it's on both the passer and the receiver.
Taking all that into consideration, I can honestly say I don't think CMS or Barnes are notably worse (or better) than anyone else in the team. Yes, they will have off days where their first touch is poor more often than not, but on average, over the course of the season, they aren't no worse.