This is very vexed question. It certainly requires the need for really experienced people but what can be perceived here is a trial by jury to see who is the better. The fact is there ain't no such thing! Unless you want a 'ghoul watching display'.
Jacko mentioned Don Bullock. That is actually a case in point. It was not a question of supernumaries being on board. It was DB responding to a call of 'can I come along?' He took 6 good people with him - some I knew personally. He asked me if I would like to go along as I stood alongside him at briefing!! I would have said NO anyway, but as it happened I was next in the display sequence. I clearly recall him asking for an extra "two mintues" of the Display Director, Simon Ames, who queried it. DB argued that he needed it to execute a barrel roll at the end of his display. The DD refused but DB did the barrel roll anyway - straight into the bottom of the valley at Biggin. It was damn near criminal in my view.
It was not much fun following that, but I did my 5 minutes - and made a few phone calls when I landed.
An aeroplane full of people in a display is an ABSOLUTE no no! Indeed, no one other than the required crew should be on board. It is sheer madness to do otherwise. The end result has often been that some innocents had their lives ended prematurely.
Sadly there have been a few pilots who were an accident waiting to happen. I guess it might remain that way.