I think that believing either in Greek or Roman gods, it would not make much of a difference, because gods from both mythologies were esentially the same, with some minor exceptions. As a rule however, the Romans have adapted and copied Greek gods and gave them different names. In some cases they also changed their traits, but other than that, not much else was different.
So, for the sake of genuity, I would perhaps prefer Greek gods, because they were the first gods, and Roman ones were mostly copies :)
