I played 31 civs on a large map for my first emperor game recently and got my tuckus gang-stomped by the Mongols and Zulus. Of course I modded the game to make all the units super cheap and 2-3 times faster than normal (but buildings and wonders cost the same). I was hoping to have lots of pitched megabattles, but instead I simply got butchered, losing two capitals in succession and giving away my best port city to the Mongols just to get peace out of them.
Next time I try that, it's back to regent for me.
I usta always go with the huge or large maps, thinking a bigger playground is always more fun. But after several 100+ hour games that never get finished, I'm starting to wonder what a small planet would be like.