yeah so i'm a little late to chime in but here it goes.
MassPro I agree totally with you re: that the health of the roots are very important and often overlooked. A little back story: When i was an enviro engineering student one of my professors of silviculture (think agriculture of trees) said that trees can only put out an amount of biomass DIRECTLY proportional to the root mass. IMHO, I don't think that it is far fetched to assume the same is true for MJ. I grow ALL types of plants using this principle and have never looked back.
and other misc. **...
Also, re: setups and their effect on root mass. I have my best results using a combined passive semi-hydro culture and DWC method. I use a mix of diatomecious earth(DE) and PrimeAgra in baskets with the bottom of the basket barely in the reserviour, allowing wicking or passive hydro to occur while plants root. By the time they are established, the roots are reaching the reserviour. At that point I add additional water/nutes to the reserviour to make the system truly DWC.(there's an air stone in the res the whole time) I discovered using PrimeAgra instead of Hydroton while studying passive hydro for orchids. Basically, PrimeAgra is made from a superior, finer clay that has wicking properties not found in Hydroton. The DE helps provide trace minerals and has the additional bonus of being an insecticide . I dont know why this works out better for me than just DWC or passive hydro but it does. I would venture to guess it allows cuttings/seedlings to adjust there roots to DWC with less of a shock since the process is gradual. I would love to hear if anyone else has had similar experiences.