I would say I would prefer someone with years and wealth of experience.
You learn by doing, and practise- my BO is in her 40's, and has been around horses since she was a child.
She has more knowledge and experience than a 16yo could possibly have, and even myself.
But then you get some BO's who have it for the money and don't know a thing about horses. You have to weigh up what it is you're looking for and what they provide.
I, however, wouldn't feel happy in the knowledge my horse was stabled at a yard run by teenagers.