The obvious answer is the Prot/Survivability spec, in which you sacrifice a few filler/bonus healing talents for an indefinitely longer time healing. Good luck staying alive more than 3-5 seconds in 3.1 when you're fighting anyone other than a level 24 undead prot warrior with the kind of squishy-ness the Holy oriented builds bring to the table.
My priority in PvP has and always will be survivability>all, which will be just that much more important with the majority of us losing anywhere between 500-800 health.
I was really curious about this, since pretty much my only twink is a 29 holy paladin. I even registered just to reply in this thread. But here are my thoughts.
I agree that the survivability and utility of a holy paladin are increased by speccing full protection. You lose a lot of both of these bonuses by going into holy for spiritual focus and healing light. But wouldn't it help your survivability the most if you are able to heal through constantly being attacked?
Does this make sense at all? Haha. Basically I think spiritual focus is really important, but then you lose imp. HoJ and imp. Devotion aura. So which is better?