Do five.

Both setups are brilliant.

Shamans go OOM in PvP very fast and are getting a 14.7% coefficient nerf come 2.3 (ie. 14.7% x 5...)

They are getting much more awesome lightening overload and seeing LO go off x 5 will be stupid.

Shamans:
For:
+ Insane Burst Damage
+ Can Heal
+ Totems
+ Grounding and Tremor are awesome in paticular
+ Unlimited Heroism/Reincarnation
+ Very flashy, looks awesome

Against:
+ Goes OOM very fast in PvP
+ Can only do one thing at a time, either DPS x 5 or Heal x 5.
+ Once your CL and Fire Nova is on cooldown you are sort of limited
+ Must be facing the right way for almost all DPS
+ Not very fast at levelling as a grp

Warlock / Priest
+ Heals on the move
+ 4x Soulstone, Heathstone creation
+ Dont have to face the righ way to DPS
+ Pets of awesomeness
+ Very hard and take along time to die at later levels
+ Felguard x 4? 1.1k Spelldmg, 13k Health unbuffed, 400+ Resillience, Soul Link etc etc all very acheviable and lets you tank like a god in PvP

Against:
+ More complicated as you have two diff classes, all are cloth and squishie
* Cannot do heroics, probably struggle with alot of BC instances
* Not as much burst (one shot i win CL EM NS etc)
* Most classes have a 'get rid of all dots for free button' mage pally rogue


Thats just off top of my head

I have both teams, probably going with locks/priest after 2.3 changes