Here is my take on the situation.
I use Prime. I started buying Prime and using it before I knew that I should use it - in other words, before I saw it recommended.
The reason for my initial purchase of Prime was the price vs. the amount needed. It is very economical. To be even more economical, you can purchase a 2 liter bottle of pond prime, which is the same product, just even more concentrated (one drop per gallon versus two.)
I have continued to use Prime because IT WORKS. My water has a RIDICULOUS amount of chlorine in it - to the point where if I am standing over my sink doing dishes or running water, it burns my eyes. I treat my water with Prime ten minutes prior to adding it to my tank (to be safe) and I have never seen any symptoms resembling chlorine burn in any of my fish.
Prime does convert ammonia to ammonium. The effects last for about 24-36 hours, and in my experience, do not interfere with cycling. The bacteria are still able to convert the ammonia. I have used Prime in fact to detoxify the dangerous effects of ammonia and nitrite during cycling. It has helped me to cycle tanks faster without any harm to the fish.
So, what would I do? I would go with Prime. But, I have never used the other product. So I will stick with what I know and what works for me and the fish
Kristina