Overclocker, a 3rd gen processors support faster memory speeds and offer more cache and faster system buses, so if you compare a 2nd generation processor with a 3rd generation, same speed the 3rd gen will be more efficient due to the new architecture.
The following link will provide a chart comparing the top 2nd Gen I7 Processor and the top 3rd Gen I5 processor.
http://ark.intel.com/compare/65520,52214 http://ark.intel.com/compare/65520,52214
