Need class decision advice...Follow

Both bring a lot to the group. One thing to consider, is that most 25-mans will only bring one Enh Shammy to put in the melee group for buffs. While they can put out sick damage, they bring little else to the raid. Warlock can also put out some pretty crazy damage, and it isn't as reliant on gear in the early affliction stages of raiding. You won't get by in blues, but at the same time there's plenty of easy to get purples for us.

I'm working on my Shaman recently, he's only 38 right now though, so can't speak for end game, but so far levelling him I've found having up to date gear makes a huge difference, which it didn't levelling my lock. I'm not to sure how hard it is to gear them up at end-game, if welfare epics are viable for them, or if they need some really hard to get stuff to put out the crazy damage they do. I also don't really care, as mines gonna go resto once I get to Outlands.

From what I see, Shamans bring damage, and I think in some cases a few interrupts(Earth Shock), on fights like Shade of Aran. Warlocks bring AoE, very important on some fights(Illhoof, Hydross) and can tank certain fights(Leo), Soulstone, HS and CoS/CoE(boost other peoples damage). All in all, I'd say warlocks have more utility, though damage output is arguable, I won't go there cause there's too many factors, such as which do you enjoy more, gear, raid make-up.....the list can go on.