The puissance of each FRPG
Each FRPG is capable of accomplishing many things. That's its inner "potency".
They are different from one another, but every one strives to achieve the same thing- that is, the Grand Illusion.
Every single one could fight the battle alone, could be isolated from all the others. In a sense, it would be pointless for them to be alive and active at the same time, because it is not in their nature to help one another or to fill the gaps among them.
Whereas i use a system i am alone with that system.
I am using it, relying on its full potential. Where does this lead, up to which level is an important question.
In this sense, every FRPG may be regarded as a tool or a weapon, a means to an end.
I envision an hypotetical FRPG coming from some extra-terrestrial planet and i wonder which FRPG available to me i'd choose to contrast its power and alleged fascination. This is why potency is meaningful.
"I'd choose whichever i find available at the moment", is an incorrect answer.