I use Piranha and I've been told that it's quite the same. Using both should be the best formula for seeds, sprouts and vegetative plants (mothers too). If you add some voodoo juice, it's even better. People from my grow store and from forums seem to be more inclined to use Piranha if they can't buy Tarantula with it. It seems the test gave better results in root growth with Piranha. Not doing any advertisement but it really expanded my root complexs in a minute. I did a test with clones and the results in a week have been outstanding. On my mothers I even had some roots coming off the pots from the top of the soil! But be careful at 2 things: it seems that the use of these products will slow your buds during flowering time cause your plants will still be busy to create more roots. Second thing is that if you're going hydro or aero, you should ask for the liquid product, cause the powder one can mess with your pumps. To me they are good products cause you can't overfeed or kill your plants with them, even if you would put a whole bottle into your soil/water, and I had very good results on root formation. I haven't been growing long enough to tell about the benefits of their protective actions, but I never had any pest/insects, disease problem since last november (when I started my first grow). Hope it helps, AD are not very informative about the real difference between those 2 products. TBITH