Intel Xeon E5 2689 's Advantages
Released 2 years late
Higher specification of memory (1600 vs 1333)
Newer PCIe version (3 vs 2)
Higher base frequency (2.6GHz vs 1.866GHz)
Larger L3 cache size (20MB vs 18MB)
More modern manufacturing process (32nm vs 45nm)
Xeon E7520 's Advantages
Lower TDP (95W vs 115W)