dragon-ball-meta:

Well, yes and no. Goten was born with a greater collection of these S-Cells within his body as a result of the high concentration his father had at the time of conception. Trunks was also born with a larger amount than normal, even if Vegeta had yet to actually acquire the form yet, due to the training his father had been doing to achieve that. (Both the boys, however, would still have had to train themselves to gain sufficient power to manage such a change, however, so they may indeed have inherited a touch of their strength as well.)

It then stands to reason that the Universe 6 Saiyans, being naturally less aggressive and bloodthirsty, would more easily acquire said S-Cells and be able to transform much more easily than their Universe 7 counterparts.