I've used GH and fox farm in the past. Mostly GH, which did work quite well... But supernatural definitely out performs it, and its cheaper. And like wrathchild said the fox farm trio shit fucks with the pH too much for my liking.
I run a flood and drain system, and i need my nutes to stay fresh in the res for at least 5-7 days, and i find the supernatural nutes stay fresh for the whole time. You'll notice when you mix them, your water will bubble a bit and foam, and the guy at the hydro store said its actually oxygenating the water when it mixes.
Here are some pics for you.. I still run the flood n' drain tables, but i use smart pots with supernatural's soil... Its a wicked soiless mix... The pic is from awhile ago, when i first got their bags. They still got the bags but they look different. But as you can see my girls look good! nice and consistent. Thats what i like!
Enjoy!