Intel Xeon E5 2660 's Advantages
Lower TDP (95W vs 135W)
Intel Xeon E5 2666 v3 's Advantages
Released 2 years and 8 months late
Higher specification of memory (2133 vs 3)
Higher base frequency (2.9GHz vs 2.2GHz)
Larger L3 cache size (25MB vs 20MB)
More modern manufacturing process (22nm vs 32nm)