I hope you are right about it working out. I was kind of thinking that it would be at least close to what the trees on our property do. Because of the layers of clay in our ground the first water table is only about 6-8' down and is about 6-12" thick. There is a slow flow that goes under us, flowing East to West. I found it when I dug a pond.Never tried vermiculite for the res but I'm gonna say they will grow just fine and a bit faster than your avg soil grow. You are somewhat mimicking nature with soil above and water table/reservoir below. With all the nice micro nutes that soil has and a nice reservoir for drinking you will see awesome results. I did a grow few months back with half all perlite and half soil with hydroton res...the soil plants actually yielded better.
I'm surprised to hear that the soil pots did better. Any guess as to why??