If I'm not wrong you need at least 27 participants to unlock the 6 lands.

I personally prefer the 3 lands because I have a small number of active players in my group, and we're all decently strong, but imagine like 10 people fighting in 3 lands, so 3 people per land each, and the chances of losing are high.

It's not like my opponents are terribly weak, similar power, just that we know how to counter them.

Opinions will differ from server to server. Dead servers need the 3 lands instead of 6.