Saddle pads were not intended to protect the horse from the saddle. They were originally developed keep the horse’s sweat away from the leather. The sweat will change the properties of the leather, especially if not cleaned properly after each use, and weaken it over time.
And didn’t the travelers use their personal bedding, from skins to wool blankets, under the saddle? Well, yes, it’s a handy place to store them while traveling on horseback as well as the first benefit of protecting the saddle from the horse! That left more room to hang other necessary gear and food on the saddle…one less thing banging on the horse’s back. And better yet, if that bedding was extended beyond the saddle, it could cushion the horse’s back from the load of iron cooking pots and food supplies. Think about the evolution of the utilitarian sleeping skin stored under the saddle and becoming a “saddle pad” to the modern day vast array of pads to protect horses from the saddle.
Wouldn’t it make more sense to not to need to protect the horse from the saddle? To just protect the saddle from the horse’s sweat?
So how should one choose a saddle pad in modern times?
Do your homework and feel/squeeze/grope a lot of pads before spending big bucks on a pad that may have worked for another horse
No matter the brand...check the seams and binding, front, back and middle...if they feel hard, rough-edged and unforgiving, forget it, it will rub.
The squeeze test is: if your fingers are touching through the material...forget it, it's useless, it won’t soak up sweat. Remember the purpose of the pad is to protect the saddle leather from the horse’s sweat!