So far I mostly play the game with gigantic sized galaxy but for me I think they are still a bit small.. Are these the final sizes or are we going to get bigger sizes ?
Remember The Settlers 1, where the biggest game map was so big it took days play time to get near the enemy let alone build enough forces to destroy him (and the 3 others..) I still play that game because of that.
The biggest problem perhaps would be the way research is done offcourse, if a galaxy is to big everybody could have developed the better techs / weapons / defenses by the time you can fight..