Intel Xeon D 1521 's Advantages
Released 3 years and 6 months late
Higher specification of memory (4 vs 3)
Higher base frequency (2.4GHz vs 1.9GHz)
More modern manufacturing process (14nm vs 32nm)
Lower TDP (45W vs 95W)
Intel Xeon E5 2420 's Advantages
Larger L3 cache size (15MB vs 1.5MB)