So I started off with DayZ, played it for a day (or rather, an hour or two)... and stopped. The amount of hackers makes the game impossible to play. Not because they kill you, but because they spawn near everyone and give out the magical equipment boxes.
Instead, I switched off to ArmA. Played on a Domination mode (Players vs AI) and some kind of Warfare mode (PvP) - in here, your team gains money from capturing towns and killing enemies, and the elected Commander spends these monies on buying airfields, barracks etc. You start with default gear and can buy new weapons, and also can buy AI teammates and cars/choppers etc.
The Domination was more fun, particularly because the game actually gave you a decent amount of vehicles and choppers, so instead of having to travel 5+ km on foot for an objective, and then run somewhere else (because the aforementioned town was captured without your help), you could fly there or at least take a ride. Nevertheless, at least you could feel the teamplay that was going on, Battlefield 3 certainly lacks in that prospect, no matter what the anti-CoD 'cool' kids say on YouTube.