Really the game shines so much more on smaller maps. Raids and drops are so much more powerful. T1 and T2 are actually used for a significant part of the fight and not everything comes down to massive T3 air spam. Big maps are just a stall fest until someone can build a game ender.
Seton's is about the largest map that is enjoyable and it gets away with it because although the map is 20X20 the naval and front spots are actually way closer together.