Intel Xeon E5 1691 v3 's Advantages
Released 5 years and 6 months late
Higher specification of memory (2133 vs 1066)
Newer PCIe version (3 vs 2)
Larger L3 cache size (35MB vs 8MB)
More modern manufacturing process (22nm vs 45nm)
Xeon E5540 's Advantages
Higher base frequency (2.533GHz vs 2.5GHz)
Lower TDP (80W vs 135W)