It really depends on the cosmology/universe/world and the other gods and their ideas and powers and all that that goes along with it, as well as, as @Yellowdog mentioned, what you mean by god versus demigod.
And, since you’re talking about changing from a 21st Century mortal human into a god or demigod, well presumably any such being/principle/concept/force-of-nature/aspect-of-existence/whatever-you-think-a-god-is would have its own perspective, personality, values, ideas, likes, dislikes, passions, etc., which would transform the value system used to make the choice.
Like if I were a pig, I’d probably LOVE being given rotten human food. So one might think to consider which god or demigod seems to be enjoying their own existence most.
Or, some completely different consideration. Seems like an unanswerable philosophical overly-broad question as written. I don’t know what you mean.