if you wanna do PvP then Stormscale hands down (Cyclone Battlegroup)
if you want a newbs Battlegroup then avoid any server on Cyclone (most of english servers starting with "R" or "S"), or you'll get raped before 1500 arena rating without a proper comp :P
what is "best"? Highest concentration of uber-rated players? Best/fairest world PVP, aka one side doesn't outnumber the other 9 to 1? Decent population, without risk of sudden 2k+ queues when you want to play?
I could go on, but I hope you get the idea.
Whining about WoW since closed beta.
Retired from WoW since patch 4.0.6.
Someone mentioned earlier that Outland was decent and Grim batol was good....... plx mate get ur facts right, Grim Batol is shit n aint got nothing on Outland atm :/
Anyways, i would go for Outland or Auchidoun