I say younger because you get to train it
I believe it really depends on how you are jumping, i’ve had both, to start horse riding I would buy an older one and when you are more experienced a younger horse
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.
But I tend to like younger horses, since you have more time with them, but not too young, not too old, like 7-12
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