After researching it seems that the hv battery could develop issues due to inactivity/non use. Given this information would buying a new 2012 from the dealer be a bad idea even if the price is a little cheaper than a 2013?
+1 Check out someplace like KBB.com (Kelly Blue Book) and put in something like 5K miles on a 2012 and the same 5K on a 2013 - I would say that if the cost spread being offered by the dealer wasn't equal or greater, then pass on the deal.
Nothing wrong or significantly different between the '12 and the '13. Use the perceived age of the car and its worth in the used car market to negotiate the price down, then keep the car for 10 years until the value depends on condition and not so much on age.
How old is the '12? If it was manufactured late in the year, it might not be as old as you think it is. Also...as noted above the hybrid components are covered by a longer warranty - especially if you live in a CARB state. No worries.