Intel Xeon E5 1620 's Advantages
Higher base frequency (3.6GHz vs 3GHz)
Lower TDP (130W vs 140W)
Intel Xeon E5 1660 v3 's Advantages
Released 2 years and 6 months late
Higher specification of memory (DDR4-2133 vs DDR3)
Larger L3 cache size (20MB vs 10MB)
More modern manufacturing process (22nm vs 32nm)