I'm currently using the HP. First time using this stuff and I absolutely love it. When I was in solo cups I had to water EVERY SINGLE MORNING but now that im in 3 gallon pots, I water a gallon per plant and it doesn't dry up AS quick. Averaging about 3-4 days between feeds now. & that's under a 600w metal halide bulb sitting about 20 inches from the top of the plants.
I can honestly say I don't think I would use anything other than the promix hp now. I love it! My only issue with it is that I have a few gnats here and there and I don't know if it was contaminated from factory or from just sitting out in my local garden center. My guess is the latter, but other than that it's been great so far.