I just finished leveling 4 x Druids (all balance), hitting 85 a few days ago, though my focus has been on instancing and I have not yet taken them into BGs. I also have a 4 x Shaman team (85 weeks ago).

I'll share what I can with a focus on PVP. My personal preference between these 2 teams is for the Druids. The downside to 4x Druids as I've experienced, having to heal means you loose your shape shifted form and thereby a huge armor bonus, not to mention a precious GCD. As has been previously mentioned buff diversity is a bit lacking. But the upside to this team is multiple HoTs, stealth, travel form.

Going forward into MoP my preferred team will either by Druids or Hunters.