From what we've seen in the games so far, I have more confidence in Jones moving the chains than Newton. It's a surprise when we get to 4th down with Mac, but kind of expected with Cam at some point in a drive. Now, maybe in a real game Newton will rely on his legs more to get that 1st down. But Jones appears much like Brady in terms of being a 1st down machine.
The one unknown is recognizing defenses. Preseason is mostly vanilla defenses. Belichick may want to devote the first few weeks of the RS to be a learning opportunity for Jones to watch situations and what these defenses do, and to see the weekly routine, feeling our record will be the same after the first few games either way.
But on the other hand, our offense provides some matchups that can't be stopped very easily, it's not like Mac will be in the same situation as Cam was last year, trying to will the impossible. So it wouldn't shock me to see Mac get the call.