TL / DR: Play what you find fun. For me, that is PVE servers only.
PvE all the way here. Played my first 3 years in WoW on a PVP server and hated getting ganked all the time. It doesn't change when you hit 80, there's always pairs of opposite faction (I was Alli at the time, so in this case it was Horde) that come across you out farming alone and waste you just for the hell of it.
Back in vanilla wow, friend playing a 60 rogue, and me on 60 priest were questing in EPL and a 60 lock rides up the path, jumps off and instantly kills us both. In TBC, I'm on my priest now 70 and diff friend playing his 70 lock and we're questing in netherstorm, 70 hunter drops of his mount and instantly kills both of us.
Finally got smart, rolled horde on a PVE server and I've never died in a world PVP fight since, unless I choose to participate via BG's, wintergrasp, etc. I like the control over when I die and have to corpse run/re-clear area/re-start an excort quest or w/e.
Lastly, i'm also a real loner ingame, almost always questing or leveling by myself, never been part of a real guild (playing together or raiding together) - one of the reasons I enjoy multi-boxing so much. This is not the way to be happy and successful on a server where ~15,000 opposite faction players will waste you instantly, on sight, just because you are there.
Those players all seem like they have more time to play than I do, so they end up with better gear than me, which makes it that much harder to take them down even if I get the jump on them. Or they had epic flyers back before most everyone did, and chase you down and do the multi-trinket Pyroblast insta-kill mid-air then slow fall down and run off laughing at your broken corpse, hanging in the sky to high up to reach so you are forced to spirit rez.
I guess I just don't play hard enough / long enough to be on the breaking edge of the content/gear wave, so I'm always waving my quest blues at an enemy who annihilates me with the latest and greatest stuff that I don't have access to because of how I choose to play my game, and because I prioritize wife, college/homework, and job attendance over playtime.
***Sorry to everyone here, re-reading this I realized it turned into quite a little anti-PVP rant LOL.
I play PVE, because I don't have fun playing on PVP servers. But that's just me :)
