I prefer chat because it's a much easier way to make fun of n00bs. just one typo and I can be like "LOL SUP N00B LERN TO SPEL". whereas if I do that on the forums I'll get yelled at by Leeza.

and chat provides me with a good medium on which to talk to my friends. because I don't have all the PM space that all my friends do (because most of them are CKs wtf), plus I prefer the chatroom setting to a one-on-one conversation through private messaging. et cetera.