Xeon L5639 's Advantages
Lower TDP (60W vs 135W)
Intel Xeon E5 2666 v3 's Advantages
Released 3 years and 9 months late
Higher specification of memory (2133 vs 1333)
Newer PCIe version (3 vs 2)
Higher base frequency (2.9GHz vs 2.133GHz)
Larger L3 cache size (25MB vs 12MB)
More modern manufacturing process (22nm vs 32nm)