Re: 2011 Sprinter Reliability
No significant difference between the 2011 and 2013 model year Sprinters that I'm aware of. Both are well into the second generation production span and past the early NCV3 teething problems in 2007 and 2008. Both have the very capable OM642 V6 turbo diesel with DPF and DEF emission systems and resulting idle restrictions and ultra low sulfur fuel requirements.
I would say choose based on individual vehicle condition and option preferences. They should have the same mechanical core. The 2014 model year introduced a twin-turbo 4 cylinder diesel and 7 speed transmission for better fuel mileage, plus some electronic safety options.