Superthrive and Thrive Alive (which I prefer) is mainly horticultural vitamin B-1.
Superthrive adds "secret hormones"; I don't use it because I want to know what's going into my plants.
I also don't like Superthrive because the label makes you think it's the only nutrient you need and I had several dozen plants that suffered when I tried to use just Superthive.
Thrive Alive lists all their ingredients, and is usually cheaper.
Vitamin B-1 encourages root growth and has a few other benefits, but your plants can do just fine without it.
I only use Thrive Alive when transplanting.