I have no preference. I’ve had both young and horses. Both can give you good and bad experiences. It essentially depends what you’re looking for in a horse. Really, you just need to try out horses and find what worms for you.
It honestly depends on what you are looking for, because older horses can teach you, but you would have to be more experienced to train a younger, green horse. And age isn't everything; I have seen older horses act like big babys