Pro mix is just a base really. It doesn't have anything in it. You would need to add everything the plants need in straight pro-mix. It isn't a bad thing, it just doesn't have any food in it unless you add it via nutes or amendments. FF has food in it, but not enough to take you through flower. Any way you look at it, you will need to feed with either choice. Since there is no food in the Promix, it is easy to NOT over feed them. Some grower really like that approach. If I was going to buy a bagged soil, I would go for the Roots Organics and possibly mix that with a bail of Promix if I wanted to include some food. I am gonna go straight promix on my next run just to try it out and step up their food. It should give me a lot of control over the PPM that they have.