Intel Xeon E5 2666 v3 's Advantages
Higher specification of memory (DDR4-2133 vs DDR3)
Higher base frequency (2.9GHz vs 1.8GHz)
Larger L3 cache size (25MB vs 1.5MB)
Intel Xeon D 1581 's Advantages
Released 1 years and 3 months late
More modern manufacturing process (14nm vs 22nm)
Lower TDP (65W vs 135W)