I would say the best compound for continued mass development is nandrolone.
No acne,no hair loss,no blood pressure through the roof(assuming you take it with TRT test),and more powerful MG for MG imo(unless you throw GH in the mix)
Now if you are not acne/hair loss/blood pressure prone and are willing to take 2-3grams and add GH, then yeah test will be better.
Tbh, there are only 5 compounds aside from peptides and GH to choose from to answer your question... Test,Deca,Tren,Anadrol,and Dbol. Anadrol and Dbol are orals and you obviously can't continually take them. Some argue you can take tren all the time... which I don't believe, and even if you could it truly does not pack on muscle mass like Deca does. This really narrows it down to Test or Deca for longterm continued muscle development IMO. The other 3 are just things you put in and out.