Intel Xeon X5670 's Advantages
Higher base frequency (2.933GHz vs 2.9GHz)
Lower TDP (95W vs 135W)
Intel Xeon E5 2666 v3 's Advantages
Released 4 years and 8 months late
Higher specification of memory (2133 vs 3)
Newer PCIe version (3 vs 2)
Larger L3 cache size (25MB vs 12MB)
More modern manufacturing process (22nm vs 32nm)