Xeon E7 2820 's Advantages
Lower TDP (105W vs 140W)
Intel Xeon E5 1680 v3 's Advantages
Released 3 years and 5 months late
Higher specification of memory (2133 vs 1333)
Higher base frequency (3.2GHz vs 2GHz)
Larger L3 cache size (20MB vs 18MB)
More modern manufacturing process (22nm vs 32nm)