I really can't elaborate much either but here is my opinion based on my experience...
The places that I had worked(on the west coast) had a base of decomposed granite laid and packed. Then a layer of about 4 inches of washed sand. The washed sand doesn't have a whole lot of dust, will not break down as fast to create dust(or slick mud when very wet) and it is easier to push through when sliding. Maintaining was so very important, the teeth always at the correct height to fluff the sand but not rip the base and so on.
In TX I dealt with with more rodeo arenas. Usually a clay and sand mix. Too much clay and it is either too slick or sticky depending on the moisture content. Too much sand and it can be hard to run in and cause strain. A clay base can be used for a half-assed reining arena if it is packed and smoothed correctly then sand fluffed over the top. But I think the DG to be the best base.
I DON'T LEAD 'EM AND FEED 'EM, I RIDE 'EM AND SLIDE 'EM.