My 2 cents on the nutrient discussion, if I may....
What everyone said here is mostly correct, in my opinion.
I started with botanicare, then went to GH, then to dutch master, then to advanced. Every nutrient line I tried, seem to yield better than the previous one. Why? Because I kept getting to be a better grower. If you picked one of the 4 brands and told me I had to grow with it forever, I wouldn't really care. I would do fine with any of them, and so would you.
If you know me, you know I grow perpetually. Each plant is a harvest. I run 3-4 plants in flower all the time so I harvest every 2-3 weeks. Doing it this way, catapults your experience ahead of the other guy who flowers an entire room out every two months. With a perpetual grow, you literally get 4 times the experience in the same amount of time. When you grow the same genetics over and over, you get to know it, and you get to "fine tune" it. Only then you can someone tell if one line really out-performs another. Honestly, I can't tell you that any of the 4 lines I've run, have any exceptional advantage over the other.
The way I see it, it's 75% green thumb (no pun intended), and 25% everything else (nutrients, light, temp, technique, etc). You can give someone an exact recipe, but only experience will make them a true chef.