It depends on what you want. Here's some food for thought:
http://wow.allakhazam.com/forum.html?forum=69;mid=113969141020413154;num=10;page=1
And yes, we do get the topic all the time :-P It's not possible to say which is better... but basically you can get 90% of the items each side can make by trading. Only two items per side are BoP.