personally, I have to go with eldar because of the obvious teleport builders and get in with webways. even if theyre expecting it you can usually get at least one gate in somewhere.
ig. good for defence and they have artilley to blow gates outa this world plus there troops are good when you have 9 squads all have plasma guns each and 3 commissors and make them excute nothing can pass them if backed up with some anittank :)
Tau:smokin::smokin::smokin: dont make me say why you already know
Chaos, by the time your enemy gets to your base, you're already T3.
Without at doubt, the Eldar. There are sooo many great places to put webway gates, and if you're unfortunate to have you teammates quit on you then there are plenty of places to hide.