In my eyes, this is quite unfair.
Why do i say this? No, it's not just because i'm a Paladin, but also because of one other, rather large detail. Destruction Locks burst. Currently Destruction Locks have some of the highest burst in game. It's on par with the pre-nerf ret burst if i'm honest.
They've yet to be brought in line ("Yo dawg, globalling someone is skillz"), and are one of the few specs that can take down almost anything without fear (despite being squishy if you can get in range). Let's compare to an Elemental Shaman.
In order to achieve burst, Elemental shamans have to first spend a global on Flame Shock, which can be cleansed (and is often a priority), and then spend a few seconds on a Lava Burst.
A destro lock has no need to do this. They're free to put on a few DoTs if they wish, yes, but they can still get 12k+ crits from Chaos Bolt on other players if geared properly. Had this been a Ret Pala, it'd have been nerfed in days. Yet here we are, a year later, with almost 0 change to the spell.
/rant off.
Others answered the question at hand though
It's better for a Prot Paladin to go into PvP with PvE gear, since the avoidance you get nullifies melee a lot, and the extra HP you get (unless you've got access to the highest tier of arena gear that is) will serve you much better than a rather small amount of damage reduction (it's only once you get into the 1K+ resillience range that it's even noticable). A trinket is still an essential though