Intel Xeon E5 2666 v3 's Advantages
Higher base frequency (2.9GHz vs 1.8GHz)
Lower TDP (135W vs 185W)
Intel Xeon Gold 6421N 's Advantages
Released 8 years and 2 months late
Higher specification of memory (4400 vs 2133)
Newer PCIe version (5 vs 3)
Larger L3 cache size (60MB vs 25MB)
More modern manufacturing process (10nm vs 22nm)