Intel Xeon D 1521 's Advantages
Released 4 years and 7 months late
Higher base frequency (2.4GHz vs 2GHz)
More modern manufacturing process (14nm vs 32nm)
Lower TDP (45W vs 105W)
Xeon E7 2820 's Advantages
Higher specification of memory (1333 vs 4)
Larger L3 cache size (18MB vs 1.5MB)