I think it depends on the subject in some regards.
If you're looking for simple marksmanship, then proficiency and ability is more important.
If you're looking at improving your tactics, I think a lot can be said for experience. Obviously they need to be proficient, but a guy with real world experience will trump a guy that may look a little better but has only done it in training.
Of course, neither matter if they can't convey the message.