Hopefully someone will elaborate on different types of footing put down because this is an area where I'm no expert except "Yeah, Looks good to run in."
Generally if the footing is deeper there is a little more cushion and more for the horse to dig in to than the shallower. On harder, shallower ground the horse doesn't have a lot of cushion and puts more strain on them.
However, it's preference of the horse too. Selena HATES deep footing. She's so little it's hard for her to get out of it and really run through it. She prefers shallower (but not slick) footing as opposed to the deep. Ruger on the other hand likes deep better.