I see more Chauncey Billup in Smart than Westbrook, or at least the Chauncey Billup prior to ending up in Detroit. Check the stats for Billups first 5 or 6 seasons. Very similar to Smart. Of course Billups kept getting better and finally broke through in Detroit as a true top player. But up to that point, he was not much better than Smart has been so far in his career.
I would say that Billups always showed more promise than Smart so I do not expect Smart will top out as high as Billups did, but to this point, it is a reasonable comparable.