I like switching it up. On Earth maps, I like to load the 24 civ mod because it's more realistic. But lately, I've been playing with the standard 12 civs on a Huge map (shuffled) or standard with 6 civs. I've found the game much easier when everyone has more room to breathe, but less war-like in the more fun (well, IMO) Classical and Medieval eras. I was able to slide up a difficulty level by giving a little more breathing room in the early game.
Easier? I hate the pressure to colonize more lands when I could be building my army and infrastructure. For some reason, I think the map scripts in BtS create larger maps by default, because I seem to have much more room to expand than I did in Warlords. An extra Civ or two isn't cutting it.
If all the capitals are more than 20 tiles apart, I just get bored with the game. It takes me far too long to fill in the space, and the diplomacy only really gets interesting once you share borders, are sending people across with more regularity, and your empire is already established.