Why would you not want him coached by the best coach of all time? At Duke he would learn to play defense and would be tested by one of the best schedules in basketball. Who cares about being a legend at BYU? That doesn't help you in the NBA. Now I wouldn't suggest he go and sit the bench for 4 years. So the real answer is how good is your kid. If he is good enough to actually get playing time at Duke, then that's an easy answer for me.