Over on the PvP side of the fence, you simply can't understate the thrill of the unpredictability that comes from fighting a human opponent. Does the other player have a better strategy than you? Are they just plain quicker at execution? For a lot of players, PvE is boring when compared to the highly competitive PvP world. As with PvE, this doesn't need to be a solo (1 on 1) undertaking, and depending on the game being played, it's possible to have numbers as big as the largest PvE raids. If you had to choose just one of these two gameplay styles, how would you be spending your MMO time?