Like most have stated, the reasons why PH's are so popular compared to AAS are:
1.To some extent, many PH's are 'legal'. Companies find loopholes by marketing them as dietary supplements meaning they can be picked up off a shelf in some Wal-Mart or GNC. You just can't walk in to a Wal-Mart and say, "Hey, give me dat der test e." and proceed to pull your pants down for an injection. Because they are 'legal' people feel safer buying them.
2.Many companies market their PH's as "safe"; knowing that they're even more harsh than some test or dbol. To us, we know this, but to the average person who wants to get big the words "legal" and "safe" hovering around a bottle of H-drol seems right enough to waste money. Side effects do vary from compound to compound, person to person, but generally very few people get any significant effects anyway, adding even more to their popularity.
3.Cost. Kind of debatable here, but a bottle of H-drol is a bit cheaper than a bottle of test (or so I've heard). I guess it largely depends on your sources for both things, but lots of people can say that affording a $30 bottle of H-drol "safely" and "legally" is more appealing than smuggling a bottle of test e in your shoes for the same price. Again, depends on your sources.
***DISCLAIMER***
I'm not some genius in AAS/PH, but I've done a decent amount of research to understand the popular compounds and have also read from the experts here and in other forums to say what I can say. Sorry if I'm an idiot though.
What about 4-AD from advanced muscle science?? what do yall think of that??
You talking about the RDe product from them? Isn't that the DHEA-variant of PH's? I've heard they're not worth the money and that DHEA has a crappy bioavailability/conversion rate. I can't say much about it, but I would rather spend your money on another compound or go out and find some test.