Right now I prefer DMing, but it actually goes in cycles for me:
DM for a while, and then start to really miss getting into a particular PC and having the plot unfold in front of me rather than constantly leaping between NPCs as well as the juggling act of keeping the plot coherent, which leads to...
Being just a player for a while, but then I eventually come up with some fun adventure ideas or read some of Paizo's latest, and really miss guiding the story and realizing these fun encounters and situations, which begins the cycle all over again.
If I play regularly, I typically have about a year before I need to flip to the other side of the screen. Right now I am co-DMing where we trade off about every level or so. So we'll see how well that appeases my conflicting preferences.