Sully has the better season of the two.
Bass has a better season than Kelly.
Yet of the three, Kelly is my #1 preference to keep.
My impression is that like Bass, Sully is pretty close to his ceiling.
KO just has an incredibly rare combination of abilities and size, enough to make his ceiling possibly higher, to me, even though he's not really a young-young player.
He needs to learn the NBA big man game inside to be more effective, since, at 7', he'll end up playing against 5's, one way or another...even if only on a forced-switch as the other team tests him. Adding muscle is a very, very good sign in this regard.
Can't coach height, and Sully likely runs into a similar problem as Bass (and, yes, Antoine).