Join Date: Aug 2009
Location: New South Wales, Australia
It depends on what type of riding your doing.
If you're riding with a western type saddle the saddle pad is an integral part of the saddle, designed to cushion the horse's back, as there is no in built cushioning. In an english saddle the saddle blanket is just used to protect the saddle from sweat. This means it can be thin.
If you're asking should you use an actual blanket or a special built bad, well it depends. In my experience people tend to use the actual blankets over pads, like to dress up a boring western pad. This means that the shape of the pad is most important. If you're just going to use a blanket, you need to be careful that it doesn't slide, bunch or pull down on the back. I believe you just fold saddle blankets to the right side.
I'd use a pad made for riding. They're often contoured so they aid the fit of the saddle, and are less likely to slip.