Intel Xeon E5 2665 's Advantages
Higher base frequency (2.4GHz vs 2.2GHz)
Intel Xeon E5 2658 v3 's Advantages
Released 2 years and 6 months late
Higher specification of memory (DDR4-2133 vs DDR3)
Larger L3 cache size (30MB vs 20MB)
More modern manufacturing process (22nm vs 32nm)
Lower TDP (105W vs 115W)