Two scenarios:
1. The real time temps throughout a long cook, clearly visible on the pit's installed gauge. Each time you see the temp it is either up 40*, or down 40* or somewhere in between. After the 6 hr cook is up, you take out your ribs and they are good. so you assume that the overall average was around the 225* you selected. Good for you. BUT how many times did you have to come back and look at the temp to make sure it was ok? Just that anxiety alone takes your time, and you are never really sure if there might have been a greater aberration. Also, since the control cannot detect a truly aberrant temp swing that in the end makes your ribs over or undercooked. Yes I know a good chef knows his equipment, and checks the ribs off and on, thus being able to adjust the time or temp according to the condition of the ribs themselves. Ok ?
2. The well tuned PID control, samples the set temp and adjusts the pellet rate or fan speed without you having to interfere. YES there are temp swings, but they are limited by the speed and efficiency of the PID to adjust. Also, not wanting it's owner to worry about the swings, it averages out the swings and can adjust the temp readout to a more dampened result (often able to keep the readout at the set rate). Bottom line: the great chef above invented the PID controller so you would not have to worry as much. Could visit with your guests, and have an extra beer or two. And usually end up with your cook as you wanted it and at the time you wanted. Not perfect but impressive, nonetheless.
Now which would you rather have.