I usually only PvP'd in WoW. Going through a raid once in a while wasnt too bad, but I was never really excited to do it. It was always the same rotations over and over with a little strafing and running around/through things. I loved the 40 man raids back in the day, but when it started cutting down to smaller raids, I just stopped caring for it.
I found PvP, whether I was in the best spec or not, to be more enjoyable. People have their own play styles which makes people partially unpredictable. A skill challenge for me was > gear/rotation/stay out of crap on the floor.
I used to PvP but then I realized that MMO PvP isn't really PvP, its more of a grind while you roll people with lesser gear. So I stopped MMO PvP and play games that are actually designed for PvP (SC2, LoL, BF2, etc..). I do strictly PvE now and I approach it as a hobby.
I don't do ANYTHING that makes me think I'm grinding so I don't get burned out. Even when raiding I made sure we did no grinding/farming. When we lost a tank and recruited a new one in all blues. One of the officers wanted to farm normal modes for a while to get him gear. I did not allow it and we just kept going with our heroic progression and we did just fine. As soon as we beat normal modes we went straight to heroic, no stopping to farm gear or anything. Might have helped that I played a healer too since there was no rotation to follow. Some fights we'd two heal it just because it would end faster so we could get to the next. So raiding was always interesting... until we beat everything then we quit lol.
So my rule is no grinding/farming ever. If I am, then I'm doing the wrong thing. If there is nothing else to do but grind/farm then to me the game is done time to find another one.
since all my lame ass RL friends only really play on xbox live.. it totally depends on whats on offer on my server / realm. I generally like guilds which do both.. i do prefer to pvp but i also like to have the chance to raid and pve without having to use random people from my server.