Intel Xeon E5649 's Advantages
Lower TDP (80W vs 130W)
Intel Xeon E5 2643 v2 's Advantages
Released 2 years and 7 months late
Newer PCIe version (3 vs 2)
Higher base frequency (3.5GHz vs 2.533GHz)
Larger L3 cache size (15MB vs 12MB)
More modern manufacturing process (22nm vs 32nm)