I prefer the used option. I've bought 2 guns new, and they work just as well as the used guns. It's way cheaper to get used guns, and usually they've already been broken in and passed the 'I hope it holds together' Trial phase.
Not to mention upgrades.
I got a full metal TM G3-SG1 Hybrid upgraded to 400 fps for what a new G3 A4 would have cost brand new.
Some people call them Terrorists. These boys have simply been...misguided.