Xeon E7 2820 's Advantages
Higher specification of memory (1333 vs 3)
Higher base frequency (2GHz vs 1.8GHz)
Larger L3 cache size (18MB vs 10MB)
Intel Xeon E5 2603 v2 's Advantages
Released 2 years and 5 months late
More modern manufacturing process (22nm vs 32nm)
Lower TDP (80W vs 105W)