Vastly prefer PVP over PVE.. any day of the week.
I know I'm going to be in the minority here.. and I understand that. If you look at the Arma3 servers, mostly everyone is playing Coop. A small percentage is playing Stratis Life or some other RPG (not for me). Some are playing wasteland (the biggest PvP mod right now). There are even fewer playing Sector Control or anything else PvP.
There's just something very rewarding about killing other humans in a video game. I just don't get the same thrill from shooting some computer controlled opfor, no matter how much you teach them to simulate human behavior. The combined arms is cool, working together against a common enemy is cool, but I prefer to do it in a PvP manner than PvE. For me it's all about the challenge. PvE brings many OpFor, your challenge is overcome your number disadvantage, and work together to overcome a common enemy. In PvE it's all about outsmarting your thinking opponents. They are no longer static enemy in a village, or patrolling along a route. They are making active decisions and trying to counter your decisions. For me that is a thousand times more immersive than any AI crapshoot will ever be.
What I really think is lacking right now; is cohesion and teamwork in the PvP scene. Arma2 PR was probably the best shot Arma had at a public gamemode directed towards teammwork - but unfortunately the playerbase was very centralized and small, mostly because the PR team had a much different thought process towards sharing work than everyone else.. but that's neither here nor there.
Personally, I think that if you want people to appreciate your work you need to create something new. Something that drives players to work together in one way or another, would be vastly appreciated by many. Right now the players that are playing PvE are drawn towards it mostly because of the teammwork value. The thrill you get from coordinating some choppers, attack helis, APCs and infantry all together against a common enemy. What if that PvE element could be applied in the PvP scene? I think it would drastically change peoples opinion on PvP, as mostly I just see PvErs looking down on it like it's counterstrike or BF3; something to quickly hop in, get a few kills, and hop out.
I think the main thing lacking in the PvP scene is a mod dedicated to coordinating players and enforcing teamwork. If this element can be integrated successfully I 100% believe that it will have a lasting player base, and be very rewarding.
If you're strictly asking : what do people prefer? You don't even need to make a vote. People prefer PvE in ARMA, just look at what the servers are playing and how they are populated. You will find your answer very fast.