I have the thinline ultra and I think it's a pretty big waste of money. I can't feel a bit of difference. -as far as my horses moving more freely or being able to sit the trot better or any of the claims that they advertise. Definitely not a miracle worker! I'm sure it does offer some sort of comfort and since I ride several different horses with the same saddle I do occasionally use it (it's so thin it doesn't seem to affect saddle fit). Lately i've been using a gel non slip pad and i've been a much bigger fan of that instead. Saddle doesn't move and it offers a lot more absorption of concussion. I got mine thinline new on ebay
for about $50, otherwise I wouldn't have wasted my money. 90% of the time mine just sits dusty in my locker.
Sorry, I guess that doesn't quite answer your question! I think the main difference is the ultra is thinner. But thought i'd throw my 2c in!