The Estes sand is very uniform and the perfect size. Something play sand is far from, but PFS is very close to. The Estes is also coated with a polymer/ceramic coating to prevent the silicates form causing a problem (brown algae). WAIT! Before anyone gets their underwear all knotted up over that: YES, I know that isn't always an issues and such and such said that form of silicate...and it glass is made from silicate...and on and on. BUT I have seen it happen with too many people too many times where their tank is fine, they change nothing but the substrate from gravel to a cheapo sand, and then have unbelievable brown algae problems right up until the day they breakdown and take the sand back out. Coincidence? If so that is a huge coincidence. Happens every time? Obviously not. But IMO why risk it, get stuck with effectively one color option (CALM DOWN! Yes, I know you can track down other colors of PFS if you try hard enough) for about the same cost as gravel and get a better product. The Estes also requires absolutely no cleaning at all. Cut the bag open and pour it in the tank.
Over the years I have seen many issues come up involving sands and a wide range or problems it can cause. However, IME that has everything to do with the type of sand and not sand in general. I have only ever encountered two problems with the sand I use and they re not even the sand's fault: 1-it can get in the filters IF cichlids decide it is fun to spit into the intakes. 2-If you use those driftwood mounted to slate decorations the slate blocks the oxygen from getting to the whole sandbed and creates those toxic hydrogen sulfide gas pockets you hear about. Obviously both of the issues are caused by other factors than the sand itself. Even with three inches of the sand I use I have not encountered toxic gas pockets, something I have seen happen in no more than an inch with other types of sand.
I want to clarify one thing: IF you do want to use a cheapo sand that isn't made for aquariums, pool filter sand seems to be the way to go because it is usually so uniform. From seeing people on forums and my own clients and customers, the PFS seems to cause fewer problems than play sand and other types.
I know it is a 'flaw' that my experience with PFS and the others is so limited, but I am thankful I found something so good when I first started using sand and didn't have to deal with tracking down exact types of cheapo sand, dealing with the problems that they really can cause (again, obviously not every time, but these issues do happen). And the color alone is more than enough for me to spend a little more to get a much better look, and my clients agree.