If you're refering to FLOPS you'll need to find benchmarks like LINPACK
For x86 that's pretty useless as it's a general purpose platform and will be used under various usages, yielding difference performance advantages for each architecture.
The benchmarks from Anandtech
suggests Magny Cour are more attractive (performance and $/performance) in data mining and HPC applications compared to Westmere-EP. While for virtualisation, my main usage for them, Nehalem/Westmere still excels exceedingly when it comes to running many light-weighted VMs.