That really depends on your priorities and intent. The Grand or Renaissance Commander is going to be less expensive as an acquisition, but more expensive to operate. The PC12 will use less runway, but won't stay airborne after an engine failure. In fact, the PC12's claim is that one always has a runway in gliding distance because the airplane glides so well. that may be true in Europe or the Eastern United States, but it's certainly not true in most of the rest of the world.
The PC12 is a comfortable airplane; the Commander feels like a sports car. The PC12 feels more like a King Air inside; it's roomier. The Commander is narrower, especially in the cockpit.
The PC12 is much newer, more user friendly; the commander has some maintenance quirks and difficulties that can leave one tearing one's hair out (ask me how I know; I'm bald). Neither one would be a bad choice.
If I were to choose between the two, operating cost being no object, I'd get the Commander with some good avionics.
The Commander does have a reputation for losing it's tail in turbulence. In the early 1990's there were several airframe losses (nearly a dozen) and control losses during high speed descents in Commanders, due to aileron rigging and issues associated with the Frise ailerons. The United States National Transportation Safety Board noted that operationally, most users tend to do high speed descents in the airplane to get the most utility out of the aircraft. Personally, I didn't; nor did I push them to their limits in any other way.