Intel Xeon E3 1220 's Advantages
Lower TDP (80W vs 140W)
Intel Xeon W 2155 's Advantages
Released 6 years and 4 months late
Higher specification of memory (DDR4-2666 vs DDR3)
Higher base frequency (3.3GHz vs 3.1GHz)
Larger L3 cache size (13.75MB vs 8MB)
More modern manufacturing process (14nm vs 32nm)