bro i'm guessing it has to do with how good each binds to the androgen receptors..its conversion rates to est or prog...i think the human body's androgen receptors can at a normal level support the trens 500/500 to a point but not the 1900 of halo...as for the strength gains are their it probably gives off more aggression or maybe its aar is more towards muscle contractions rather than muscle building..thats my guess..weird shit tho:scratch: