By the numbers, Dinwiddie and Smart are very similar, with the exception of Net Rating, Smart is +4.7, Dinwiddie is -1.7. The only other stat that is not fairly close is steals where Smart is 2.0/gm and Dinwiddie is 0.6/gm.
Dinwiddie doesn't shoot better, doesn't get appreciably more assists, doesn't result in more pace. Dinwiddie's scoring is down this year but his shooting isn't necessarily worse, he is just taking fewer shots. I am not sure there is upside here.
I think what Dinwiddie does is make Smart look pretty good in comparison.