So, there is confirmed to be a huge difference between the two games, designed for people with varying schedules to select whether they'd mostly like to play during the day or night. Sun runs on the normal clock, while Moon runs twelve hours displaced.

Minor differences include the cover legend, and the totem Pokémon are different as well.

So until now I was leaning Sun because the legendary looks cooler, but this made me reconsider for a minute. Interesting use of the opposite version mechanic, though.

But if, for example, you wanted to play Moon like a normal person, couldn't you just set your 3DS clock back twelve hours?

I'm getting both games.