Oh, 1 more thing I see people discussing: first turn factor.
So here the numbers:
Average of 10% more chances of winning a round were you start. Non significative difference between islands and caves (I was surprised about this, was sure the effect would be significatively bigger on islands). 95% confidence intervall: 7%-13%
Sample used: top half ONL overall ranking players, that's 14 players with at least 200 rounds played each-
It's up to you to decide whether that is big or small advantage.
Edit: there was also a positive correlation (r=0,68; p=0,01) between the advantage a player gets from first turn in caves and the advantage the same player gets from first turn in islands; indicating "how much advantage you can get from first turn" as an ability that varies from player to player.