Originally Posted by Speed Racer
My first question to you is what experience do you personally have in breeding, raising a foal, and training a youngster? If you say none, then your best bet is to buy an already trained adult.
This is the most important part. If you have the knowledge to train them yourself (or the budget to have a trainer help you every step of the way), then it's all a matter of your own preference.
Personally, since I have the knowledge, I prefer to train all my own instead of buying one already trained. With me doing all the training, then I will know exactly what the horse has been trained to do, what they haven't, what their triggers are if they have any, and they simply don't have any baggage. Whenever I ride a horse that's been trained by someone else, I'm always wondering "When will I come across the snag in their training that gets me hurt?"