i use one on my horse and i used it on my old one and i think it is probably nicer for them as it absorbes some of the pressure...but i dont know, i just like using one.
I bought one in the spring as F had dropped a bit of weight, but my OH has pinched it for S. They seem to be highly recommended - lots of posts about them before if you do a search.
My tb had a back problem and I was recommended them by the back specialist and then my saddler, independent of the back mans advise. Now I never ride without it. She certainly seems very comfortable underneath the saddle where before she could be a little cold backed.
So I have 3, an everyday one, one thats built into a saddlecloth for dressage and a third dressage cut pad which I use for showing as it's discreet enough.
I have been riding my TB this summer with just a prolite pad under his saddle as recommended by both saddler and back lady.
Because I wanted a numnah under his saddle to take him hunting I found a gp numnah with prolite pad built in which he loves. It fits perfectly and has prolite built in with a lovely soft quilted underside which I think wicks away moisture. I would highly recommend them. I got mine from 4 Dobbin. Not cheap at £55 or so but SO worth it. Mine is black and lovely!!