Sage or Priest whichever gets you comfortable.
Priest is a master of 1/2/3 v 1/2/3 not just in pvp but can also easily keep a small concentrated group alive during PVE. Compared to sages where they have to cast "Ground"[debuff] skills to debuff players and can only cast 1 ground skill at a time, a priest can easily debuff any ailment the opposition may throw. Now the drawback is that 1 debuff 1 spell from the priest meaning multiple debuffs may give you some problems however i have seen priests how have found a way to overcome the single debuff problem[i wont give out the build since they might get mad]. Anyway priests has more instant AOE heals and HOTs [Heal over Time] compared to Sages. Priests do well also with Massive single target nukers such as locks and zerks because they have Celestial Anger. At the same time priests can learn the stun from the Mage job which can really help your 2 v 2 or 3 v 3 fights.
Sages on the other hand is best suited for Huge parties and Raids. Before sages really performed well when Frigid [world boss] was still a little bit hard to kill since most players were not yet that geared. This time around i believe sages would be a very vital character on the up coming new World Boss Lost Mysterion, Mysterion will be spawned on a PVP zone so it would not only be a PVE to kill mysterion it would also mean you have to fight against players who are in the hunt for mysterion. This makes boss hunts a bit more complicated and fun. [Why hunt mysterion? he has a kewl new set that only drops from him k?

]. Also on pvp sages would no longer need to worry about constantly casting a debuff on his ally since he can just pop out a Ground spell and have that guy pass on the circle if need. The drawback on the ground spell is on PVP since opponents would not just stand around waiting to be killed. Sages have less HOTs but more on Massive Healing however most of these spells require casting. But some sages found a way around this.
So all in all they might have small differences but they do the job just the same. I suggest you pick the class that you can handle and makes you feel comfortable.
PS : Elf looks cute on a costume 3=D
Cheers!