Xeon EC5509 's Advantages
Higher base frequency (2GHz vs 1.9GHz)
Lower TDP (85W vs 250W)
Xeon 6766E 's Advantages
Released 14 years and 4 months late
Higher specification of memory (6400 vs 1066)
Newer PCIe version (5 vs 2)
Larger L3 cache size (108MB vs 8MB)
More modern manufacturing process (5nm vs 45nm)