Props for your service bud. I say consider these thoughts:
How long do you intend to keep the car?
Are you going to mod it?
Is i going to be your primary car?
Can you afford to take the hit if you bought new?
If you intend to keep the car for a long time, I would buy new.
If you're looking to mod, and keep for a few yrs, maybe just buy used.
DD - refer to my first question...
If you can afford to buy new, I say do it. Nothing like being the first one to fart in your own seat and especially after your deployment
All kidding aside, chances are if you buy used it's been beaten a little. And depending on the previous owner it could be a little more than you would think... Just search youtube for 370Z and take a look. Some downright idiots out there beating the piss outta their cars...