Yes but i think we can easily say that Barton has done more for the team than Jonas. It's Barton's deliveries that have created us so many goals, he may not get the final touch but it's him that created them.
I think Jonas has been good recently but he's without a doubt our least influencial mifielder this season out of the main four. Nolan has scored alot of goals, and been a true captain, you can see the difference without him, we haven't won a game without Barton, and his vision and deliveries has been vital, Cheik Tiote = Cheik Tiote. Jonas has been great, and i'm not denying he's had impact this season, but the others have simply been more vital than he has. IMO obviously.
You could easily buy a better winger/midfielder than Jonas, Cheik Tiote, Barton and Nolan have given us something priceless.