KG is a much higher class of player, even at this stage of his career.
I realize that stats don't tell the whole story, but here are the numbers so far this season (PPG, RPG, BPG, PER):
Smith: 15.6, 8.5, 1.7, 20.85
KG: 13.2, 7.3, 1.0, 18.45
Not to mention that Smith is considerably younger, faster and more athletic. I like KG, but his lateral quickness on defense isn't so quick anymore, as evidenced by that late play involving Nowitzki last night, and I can't imagine KG's legs/lift/quickness getting better as this season goes along. I don't want to see KG go, I'm just trying to creatively problem-solve.