An old post indicated that
custom games are player<->player
ladder games are player<->game server<->
http://forum.valhallalegends.com/index.php?topic=10902.0 (http://forum.valhallalegends.com/index.php?topic=10902.0)
My experience with Warcraft 3 is that in custom games the creator of the game has much better input latency than other people in the game. How is this so if the network model is peer to peer with lockstepping. Is there information about the protocol used for custom games?