To start I use Hydroton because it is easily accessible for me. It is carried by a local hydroponic store. I have been happy with it and use it for S/H culture as well as using it as medium, in baskets, for Catts . This medium is sphere-shaped. I have a couple of plants in Primagra, which came to me in that, Priagra is more irregular and some swear by it. I think the irregular shape gives more medium to medium contact and therefore possibly better wicking action. The round Hydroton gives a bit more airspace. Which is better...???