I agree on the velocity's "Importance" given for the FPE formula, but the power factor also takes into consideration the bullet diameter. None of the other formulae do this.
With FPE formula the vel. is squared, but not with the "Power Factor" or the momentum formula.
The Momentum formula is better I think than FPE, but does not take into consideration, the bullet's diameter.
The Power Factor gives equal weight to all of these.
Of course, bullet construction is not addressed, which is also of equal or perhaps of the most importance. Thus, there is no mathematical formula which covers all aspects needed for a "true" picture. Some, are just better than others.