This is only my opinion and it's not for argument sake, but there is not one breed of horse that is better to work on than another. Your mind set and the handlers ability come into play. I work on everything from thoroughbred race horses to a Miniature horses and donkeys, 17+ hand drafts to Paso Finos and Arabian Halter show horses . 99% of the time if you respect the horse and be patient the first few times they will get easier to work on. I never work in cross ties and sometimes even have to ask the owners to leave so that I can work on their horse. I do this because if the horse doesn't respect their owner, they will not respect you when they are around. Well there's my two cents worth!
Happy Trails and Trim safely.
"Never approach a bull from the front, a horse from the rear, or a fool from any direction."