It's referred to as equimolar potency, and it's basically how we discuss relative potency between anabolic agents. It's the least "bullshit" concept that exists – it basically "boils down" a chemical to its basic anabolism when we are discussing androgens and their respective potential to cause hypertrophy.
Obviously, at least it is for me, having done more than my due diligence of theoretical & practical work, Primo (metenolone) is less potent on an equimolar (per-mg) basis than trenbolone. This is because while metenolone is a straightforward AR agonist, subject to a sigmoidial S-shaped curve with respect to dose/response (mg vis-a-vis muscle growth), Trenbolone serves multiple bodybuilding objectives via multiple mechanisms.
Practically, this results in less pinning if using the enanthate ("Tren E") or hexahydrobenzylcarbonate ("Parabolan"), at minimum.
However, trenbolone also offers other benefits vs. the universe of androgens. It's basically the "Swiss army knife" of androgens, serving a role in Bulking (increasing muscle size dramatically by augmented mIGF-I [autocrine/paracrine MGF] activity), Cutting (reducing fat mass & increasing insulin sensitivity), or recomp (simultaneously increasing LBM and decreasing FFM), via mechanisms not shared by other androgens, thereby combining synergistically (greater than additively; 1 + 1 > 2; per-mg).
See:
Worked example for synergistic combination strategies (TMT; testosterone + masteron + trenbolone)
My forthcoming book, titled
Ampoule: Rational AAS Use and Principles of Cycle Design