People are all different, horses are likewise all different. The term "form to function" was coined to describe the concept that one type of conformation that will work for one thing doesn't necessarily work well for another. Form to Function is a cowhorse (cutting, reining, reined cowhorse) generally being smaller than a Teamroping heading horse. The size and weight of a larger horse is needed to offset the size of the steer being roped and jerked to set it for the heeler, who rides a smaller quicker horse who only needs to turn a corner and stop to stop forward momentum of the steer & the clock.

Barrel horses come in ALL sizes because the conformation requirement (speed, ability to run a turn without slowing too much and the sense to be a partner) is found in all sizes of horses. Only when the horse is extremely small or large does size matter a great deal. And in my opinion size matters if you are a large person riding a small horse in a timed event where fast starts and stops are affected by heavy weights. There will always be exceptions to every generalization, but a thinking person can see where size of rider ratio to size of horse will affect performance against a clock.

But ultimately the ONE thing that will decide the success or failure of a performance horse is attitude. With a rotten attitude they will suck at everything, with a good attitude they might be at least useful if not great inspite of a flaw or two. So one can prophesize all they want about pedigree, cite theories and claim to know, but they don't KNOW 100% without a doubt that a horse can do a job until they TRY them. I would take a flawed horse with a good attitude over a brilliant horse with a poor attitude any day. Anyone that's been let down by a sorry counterfeit sucker knows what I'm talking about. 8o