Intel Xeon E5 2609 's Advantages
Released 2 years late
Newer PCIe version (3 vs 2)
Higher base frequency (2.4GHz vs 1.866GHz)
More modern manufacturing process (32nm vs 45nm)
Lower TDP (80W vs 95W)
Xeon E7520 's Advantages
Higher specification of memory (1333 vs 3)
Larger L3 cache size (18MB vs 10MB)