I'm not saying you should not go with PID, but not all PID controlled pellet grills are designed to maintain +/-5 degree swings. There is no benefit to that kind of control so I would not list that as any kind of criteria, or you'd be eliminating some very good grills. Extremely tight control does not mean "better".
And even newer grills without PID controllers produce very stable temperatures. But I've used pellet grills that had +/-25F swings and it produced food just as good and easy as my Memphis.
No benefit??? - that's a tough argument to win