Xeon E5540 's Advantages
Higher base frequency (2.533GHz vs 2GHz)
Lower TDP (80W vs 105W)
Xeon E7 4820 's Advantages
Released 2 years and 1 months late
Higher specification of memory (1333 vs 1066)
Larger L3 cache size (18MB vs 8MB)
More modern manufacturing process (32nm vs 45nm)