If you ride a horse that needs the bit for collection (such as dressage) or a gaited horse that needs collection for smoothness in the gait, the bit may be integral to achieving that collection, IMHO the bit is more for balancing the horse than for stopping. Bitless horses string out more and that is another reason they are often penalized during competitions, and why dressage does not permit bitless since it is considered a disadvantage to the horse.
Also, while bitless is often perceived as being more ‘humane’, bitless headgear applies pressure on the bridge of the nose, the poll, and
/or the cheeks, depending on its structure, and may not be any more ‘humane’ than a bit. My gelding does not like his bitless headstall, although I had one made for him similar to the one that my mare loves, she never rides in a bit. I have also tried several more gentle bit types, but he prefers the paso spade bit (which make me blanche). Looks can be deceiving and even humane looking bits and headstalls can cause pain; hackamores have been known to break noses, nothing humane in that. The length of the shank can be more problematic than the bit itself.
For me there is no controversy, I use what my horse is most comfortable to work in. One goes bitless and the other does not. If you have to drive with a bit, it will probably not be ‘safer’ as runaway horses can think “what bit?” as easily as “what headstall?” but I would not feel “more humane” driving without a bit either. Can a better rounded horse pull with greater ease and less risk of injury to him? It is a horse-specific issue, some work better with mouth pressure than face pressure. In the end, “humane”-ness rests in your hands, not in the equipment you use.
Alois Podhajsky: “When I hear somebody talk about a horse being stupid, I figure it’s a sure sign that animal has outfoxed them. ...