Xeon E7 4820 's Advantages
Higher specification of memory (1333 vs 4)
Higher base frequency (2GHz vs 1.8GHz)
Larger L3 cache size (18MB vs 1.5MB)
Intel Xeon D 1581 's Advantages
Released 4 years and 10 months late
More modern manufacturing process (14nm vs 32nm)
Lower TDP (65W vs 105W)