Depend on what else you have, prot pallys atm > every other tank bar none. They have better survival and good threat, however warrior tanks are much higher on omen if both are similarly geared and hit capped.
I have nowhere near the level of survivability a pally has, but I can out-threat them like a motherfucker.
Saying pally buffs are better than boomkin buffs is not true, it is often true but if your 10 man group has caster heavy dps, the boomkin becomes rediculegood. Freya 2 elders 10 man for my guild was 3 mages a lock and a boomkin, prot pally holy pally druid healer, dps warrior and me. It was pretty effective on burn stages and nuking lashers.
Disc priests in 10 mans are obscene. 25 man holy wide raid healing is sick, better than restro druids even but 1 druid for motw and a battle res is nice. There is no best group, but 10 man combinations based on these may work nicely.
Prot pally - Awesome survival, Bosanc on other tank, BoW on casters, death cheating AD,
Prot warrior - Commanding shout, thunderclap, demo shout, sunders, threat like a depressed nuklear technician, Unfearabletonk(psychic scream? fuck you, shield bash.), stuns.
Disc priest - stam boofs, shields on the entire party, fear ward
Holy pala - BoK/BoW/BoM depending on what the prot pally is doing, resistance auras
Resto shammy - hero/BL, good raid healing and single target healing, totemz (OMGTREMOR)
Destro lock - SS/Summon/lockrocks/good dps
Mage - Int... food? Portal at end I guess...
Hunter - Crit crit crit/nature res
Arms Warr - bleeds, battleshout
FeralDPS - battleres, bleeds, MotW, FF
Boomkin - Battleres, MotW, spell crit, FF
Blah blah blah.
More than 3 pally is overkill, but one is enough for BoK. Priests for stam buffs, shamans for hero/BL, not many other classes bring this much to the table.
Melee dps go well with melee dps (Mixing bleeds, armour pen on sunder) and casters go well with casters, (boomkin aura, arcane int etc.)
Just realised how many times I used the word "depends", because it really does. If a spare warrior can do BS why use BoM? If there is only one warrior and no pally, BoM and the lock can use imp blood pact etc. etc.
Obviously I value some classes over others, but that is just from grouping with them more.