RDPS: hunter or warlock?

So I've been having troubles debating which class is typically better. Warlocks are well known in TBC for top chart damage and it usually only gets better: however, I've been seeing some hunter forums and videos showing that hunters are well capable of outdoing warlocks and have experienced it in a few karazhans myself. What class is more "needed" in the sense that you see a lot more people asking to bring it, and which one usually is just better?

As far i have seen both are great dps - there are alot more hunters then locks so you can't go wrong with lock.