Good question. The difference to me is longevity. I originally got their regular or medium pore stones, and have switched to the fine pore a few months ago when I built the new manifold.
Prior to that I had wood stones. The wood stones can actually put out a finer bubble, but need to be replaced fairly often. The Aquatic-Eco fine pore stones gave me a lot more stone surface area (I am now running 8 x 9") so more air into the skimmer, but with perhaps slightly larger bubbles.
The big deal is that they can be cleaned and re-used, giving them an excellent lifespan. All I do is pull the manifold out about every 6 months and soak the stones in a weak muriatic bath.
As far as skimming goes, switching to the Aquatic-Eco stones did up my skimming, but that is not a direct relationship since I increased the stone sizes significantly. If I had say 20+ of the wood stones, they might skim as well or better. BUT, wood stones turn to mush in a couple of months or so.
HTH!