Randle and Smart have each played 28.4 mpg in their careers. Smart is averaging 9.3 p, 3.8 r, 3.7 a, 1.5 s, 0.3 b, 1.6 t, 2.7 f on 42% from 2, 29.1% from 3, and 76.2% from the line (2.6 attempts). Randle is averaging 12.2 p, 9.4 r, 2.6 a, 0.7 s, 0.4 b, 2.1 t, 3.1 f on 46.9% from 2, 27.3% from 3, and 71.7 % from the line (3.6 attempts). Smart is a much better defender which doesn't show up in the stats as much, but there is a pretty clear statistical advantage to Randle.
yea you are literally comparing one of the worst defensive players in the league to one of the best. Putting these stats together is kind of like trying to argue Hollis Thompson has better stats than Bruce Bowen except for defense.
The difference isn't that big either, the rebounding edge is there, but otherwise Randle just comes across as a guy who takes a few more shots a game. More turnovers is especially glaring as Smart handles the ball heavily.
42% from 2 three years into a career is at an all time level of ineptness though and because he shoot so many 3's his overall FG% of 35.8% is even worse. I haven't looked, but I can't imagine there are many players in basketball history worse than that, if any at all. For a comparison, Allen Iverson, a well known inefficient chucker, only shot below 42% from 2 twice in his career (41.9 and 40.

and was never below 43.5% in any other season and ended his career at 44.8% from 2. Of course AI actually got to the line at almost 9 a game for his career and was carrying a heavy offensive load.
Smart has been the better player thus far in their careers, but the fact that he is still this bad offensively does not bode well for him going forward, especially playing for a winning team where he should be held accountable for his terrible play. Really hard to gauge what Randle will end up like given he missed basically his entire rookie year with an injury and has played the last two on a terrible team and coming back from that injury. Ingram, Russell, Clarkson, Williams, Young, etc. aren't exactly what you would call a defensive force in the backcourt and on the wings. So the question is more, is Randle that bad defensively or is it just a team situation. But Randle showed great strides offensively last year. Increased his FG% a lot, got to the line more, developed into a solid passer (3.6 apg), and expanded his overall game.