Just to finish up here I'll throw my personal opinions around - remember these are simply based on my experience as a whole.
Vash'jir: Prot > Ret
Hyjal: Prot > Ret
Deepholm: Prot = Ret
Uldum: Ret > Prot
Twilight Highlands: Prot > Ret
Tol Barad: Prot = Ret
I literally have zero experience questing as Holy so I cannot speak for it. I will say, also, that Protection continues to be easy-mode throughout all these zones more-so than Retribution, however Ret's killspeed on 1 or 2 targets vastly exceeds Protections near the closing levels of 84-85.
Regardless, this whole expansion seemed pretty easy as either. If one ain't workin' give the other a try, but both should get you through =)
Warning - Attempting to patch together any coherent message from my posts may result in chronic headaches and/or intense vomiting.