Here because you assimilate communism to stalinism. One could be defined independently of the other. Did Karl Marx organize the Gulags in Syberia? Did Josef Stalin organize the end of the state? I am not sure.
It is possible to think the differences whether you leave the ideological categories created by the context of Cold-War.
Then, I am not claiming that any is preferable. I am asking for further precision in the way to use words which have a history.