Hi Ashraf, I don't know about the differences, they both have the same abilities - drainage and air effect.
Perlite does infact retain moisture but dries out very quickly. I once grew out a couple of phals seedlings, they did well. But, the watering was too much - a few times aweek in fact. The roots we're beautiful, just couldn't keep up the watering and fertilizing routine.
Coupling sphag and perlite is the best way to go for me.
