Hi welcome,
If you aren't going to mod or track your car, then you should be okay with a 2011. The 2012 comes with an oil cooler, and some other minor changes and options that Nissan offers. Read here:
2012 Option List Includes Dealer-Installed Performance
As for the pricing you should be able to get a base 2011 for around 33-35k OTD, I purchased my 2011 in July, the prices were still competitive then, so actually you can probably do better if you are planning to buy in December, you should be able to get away with a pretty good deal, like lower 30s. Now you can still try and get a base 2012 as pricing is not that much different. All in all if you are planning to just buy your car to drive not modding or racing (although you will be tempted to mod), and are working with a budget I would say go for a 2011, nothing much has changed for 2012.
If you want some more info on the 2012 here:
2012 Nissan 370Z to Start at $32,210 - WOT on Motor Trend