i have an ogilvy and a thinline. one of my horses did not respond well to the ogilvy while the other loves it. i use the thinline for my eq horse and it's super supportive. when i would get on with the ogilvy, he would sink back. with the thinline, he doesn't at all.
ogilvy is my favvv, a lot of ppl say the memory foam does nothing bc it "deflates" but i have the 1' and it does wonders w my horse who has a terrible back. i also have the gummy half pad, which is amazing too, however these are both more expensive options.
thinline is a good brand, and their most basic pad is rather inexpensive. . .i definitely recommend looking into those & seeing if they will do good for your horse.
Kavallerie is my personal favorite, I have one for my horse and he seems to really like it. Oglivy memory foam pads can squash down and then it doesn't do much of anything- gel is better IMO. ACavallo is also really nice.