I'm wondering if anything new was developed for the 2013s, or if the differences between 2012 and 2013 (I assume there are always some) are superficial.
I notice you posted this in the Prius v forum but you mean the Prius Liftback. The changes are very superficial if any. The mid-model facelift was done on the 2012s. If you are looking at 2012s then make sure you are getting a super discount otherwise you are losing money because that car is already a year old and trade-in values will be lower than a 2013 with the same number of miles.
Vehicle Proximity Notification System (VPNS) was added as standard on the Prius v wagon for 2013. If we had known, we would have waited for it instead of buying a 2012 a few months earlier.