Intel Xeon E3 1220 's Advantages
Higher base frequency (3.1GHz vs 2.9GHz)
Lower TDP (80W vs 135W)
Intel Xeon E5 2666 v3 's Advantages
Released 3 years and 7 months late
Higher specification of memory (DDR4-2133 vs DDR3)
Larger L3 cache size (25MB vs 8MB)
More modern manufacturing process (22nm vs 32nm)