Well... Its fun to think as effectively as possible in this game. What you gain? Game play time reduced!
Hints: Think how to cover a sphere's surface with the number of bases you want effectively, but watch out how game mechanics (continental land coverage, nation borders, ufo lost at sea etc) influence the best placement of your base.
You will realize soon enough through the game mechanics as they reveal themselves to you while you play, if your base is in a good spot or not.
But after all its a game! ^^ Just enjoy and have fun wherever you put your bases!