There are many opinions on what makes a good horse in terms of genetics, structure, attitude/disposition, training, etc. One of the most crucial aspects is conformation (how body parts are put together). Even if a horse has a popular pedigree, amazing personality and willingness to perform, if he doesn’t have proper structure for his job –whether pulling a cart or competitions that require athletic agility--and durability, he probably won’t do well and may go lame.
When selecting a horse, make sure his structure will hold up so he won’t go lame or become unsound. Second, choose a horse that can excel in the discipline you enjoy. A draft horse well suited for pulling might not make a good riding horse, and vice versa.