It may depend on what you trying to protect with your pad.
I have a horse that has a Thoroughbred bred build and is hollowed out behind his shoulder blades which causes pain because the saddle settles in the hollow and pushes on the shoulders. I have been recommended the Bio-Fit like Drum said, and I love it. You can get it in the felt bottom or fleece and different sizes and thickness. Well worth the money.
I have also the Professionals Choice version of the pad and I find it slightly awkward because of where the extra padding is placed for the shoulders. Because of the "slack" over the spine for airflow can make the pad difficult to get exactly right on both sides because of how I adjust my pad after I place my saddle on the horses back and pull the pad up off the withers so it doesn't bind up. So again I haven't found that to be a problem with the Bio-Fit.
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.