If we are trying to build/shape a swing I want high volume reps on the range. If we are trying to play the game then getting on the course is better. However this depends on your situation. I am at a very nice Public Facility that has a lot of rounds played. Getting out on the course for a playing lesson can be very difficult.
What I try to find out from both the player and parent is problem areas during their last round or two.
If the problems are green side we have a great short game area to replicate the situations.
If the problems are more full swing oriented we have a nice sized range that we can visualize/replicate where they are struggling.