for showing, though I also have a white contoured dressage pad (with Mattes half pad built in) for showing, and at home I use a nice, used, stained contoured dressage pad (with a Mattes half pad under it.)
I have short legs and don't need any more material between myself and the horse, or between my whip and the "area behind my leg", in case the horse needs a reminder to stay in front of it.
The dressage judge couldn't possibly care less, so whatever suits you and your horse (and floats your boat.)
"Hope is a good thing, maybe the best of things, and no good thing ever dies."
"It's supposed to be hard...the hard is what makes it great!" (Jimmy Dugan, "A League of Their Own")
I am cheap and haven't invested in a fitted dressage ped, so at unrecognized shows I use JUST the half pad. Nobody seems to care. I do break out a square pad for recognized shows, albeit one that's got a very short spine length so my 15.3hh horse doesn't swim in it.