The preperation Deca-Durabolin shows a much lower tendancy for estrogen conversion...For comparison, the rate has been estimated to be about 20% of that seen ith testosterone... This is because while the liver can readily convert nandrolone to estradiol, in other more active sites of steroid aromatization such as adipose tissue nandrolone is much more resistent to this process...estrogen related side effects are a much lower concern...An antiestrogen is likewise rarely needed with Deca...
Deca also lacks the 19th position carbon atom (19-nortestosterone)...which gives it much weaker androgenic properties...
Primo:
An enanthate ester is added to the steroid, which causes a slow and gradual release from the site of injection...Its duration of activity would be quite similar to testosteron enanthate, with blood levels remaining elevated approxmately two weeks...Methenolone itself is a long acting anabolic, with extremely low androgenic properties...The anabolic effect itself is also quite mild, its potency considered to be SLIGHTLY less then Deca on a milligram for milligram basis...
So you are pretty safe using either one...Hope this helped a little...