I think the difference from my perspective, is that Smart can play right away. I couldn't find any PG prospect in the past 10 years that was as NBA ready as him and that couldn't. Harris is much more questionable, but we could bridge the gap with the MLE or some other pickup.
That and just in terms of veteran talent: Kevin Love, Jeff Green, Chandler Parsons, Omer Asik, Brandon Bass.. that's 5 players who can legitimately start on a playoff team and at least 1 All-Star.
IMO =).