At the moment retrdins are ridiculously strong overall... and boring. They have very few skillshots compared to subrogue, so you probably will get bored of it in the leveling process unless you don't mind to auto-attack and not using more than 1-2 buttons until level 50 (not that later you're using much more buttons, though). On the other hand, leveling a rogue is a pain in the *** the first levels; you can find even difficult fighting two mobs at once.
I am a PvPer myself, I've played the two classes thoroughly on wotlk servers and I would choose rogue. They are Much more funny to pvp with, require more attention/skill and will always work on many arena teams. There're just too many paladins out there, one more wouldn't be noticed.
As a rogue, if you're loosing the BG, you can always hide and ambush the distracted players. Sometimes you can even win the BG assaulting the last AV tower when nobody's there. And the CC. I will always love the fact that you can have anyone looking at the screen for 20 (or more) seconds without moving. And shadowdance. Everybody loves (or hates) shadowdance.
Paladins do absurd high damage with three buttons, can heal easily and have a lot of survavility. But once you get to 80, healing as ret is not a win-card anymore in arena, you have to use wings wisely (else you will get focused and die due of the lack of inmunity), you don't have an interrupt nor a healing-reduction ability, many people will dispell or steal your hand of freedom... You will still1-shot many low-geared players in BG, but you can do that as a rogue too. And hide, and repeat.