Xeon E6540 's Advantages
Higher specification of memory (1333 vs 3)
Higher base frequency (2GHz vs 1.8GHz)
Larger L3 cache size (18MB vs 10MB)
Intel Xeon E5 2403 's Advantages
Released 2 years and 2 months late
More modern manufacturing process (32nm vs 45nm)
Lower TDP (80W vs 105W)