Interesting comparison. Generally we match up riders/horses taking into consideration skill level & ability of rider with temperament & training of the horse. And then add in the component of what the activity will be. I think you could generally do that with skier, skis & what the skiing activity for the day will be. Remember that "average" riders do ride averag Arabians and Thoroughbreds. They just need to be matched up correctly. Riders progress, some horses are already at the top of their progression. Horses also progress, but may need a rider more skilled than the horse to continue the progression.
You aren't going to put a new rider, still developing balance (really important ), strength & skills on a horse trained for fast,quick moves, reactive to the slightest communication (thinking cow horse,cutting,reining here, or a contortionist speed jumper), you'd put them on one that requires a bit more encouragement or firmness so they don't end up on their butt unintentionally. One of those nice school horses that says "do you really mean that ? oh, ok then."
But there always comes the time when a rider needs the challenge of a different horse in order to progress in their skills. Or a variety that requires development of versatility. Like a short strided quick pony requires great fore/aft & lateral balance, quicker reactions for the shorter stride, than say a long strided Thoroughbred w/some lofty bounce requires subtle fluid riding.
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