Its a very interesting question. If your game was very unique you can probably release now/update later, btu it sounds like you are in a very crowded and tough market.
If you actually want portals to take the game, I'd strongly advise making it perfect before submission. They are swamped with chocie and probably will not look at an updated version later. Even though Realgames did take Starlines, and it still sells, they wont take Starship Tycoon which is the same but better.
If your planning on selling it direct, maybe you could try an early release, it will help you to get feedback on what's good and bad.
Its a tough choice.