Sage System vs Nash Equilibrium

A friend pointed out to me about another possible system of playing Heads-up endgame in SnG. It is known as the Sage system.

Basically, in Sage system, a Power Index (PI) is assigned to every value of R (ratio of stack size to blinds).

PI = [(power number)x2] + face value of smaller card + Y

Where power number = rank value of different cards (A=15, K=13, Q=12 ... 2=2)

Y = additional points (suited card = 2, pocket pairs = 22)

So, say I have 67o, at R=7, should I push or fold?

Nash says, I can push this hand profitably whenever I have ~10bb.

SAGE says,  PI = (7*2)+6 = 20 which is a fold according to SAGE!

Hmmm.... both are based on math but they gave different recommendation....

This will be my research topic from today. Understand the difference between Nash and SAGE and decide on which system to choose.