The architecture in the 2010/11 is 100% identical to the 2012/13. There is no difference internally. The only difference is the year of manufacture. The chassis (case, power supply, logic board, and processor board) are a couple years newer on the 2012/13. If performance is most important for you while maintaining a budget, go with the 2010/11. If you want the absolute latest, go with the 2012/13.
Please note that regardless of the year, we only acquire systems from larger studios and corporations. The systems are utilized in air-controlled locations and are shut down / put to sleep after hours. Plus, we clean and test each system thoroughly.