I am working on pricing out 4 Dell R710s for a new Hyper-V cluster. I have a choice between the following two configurations, for the same pricing:

128GB of 800Mhz RAM per node

Or

96GB of 1333Mhz RAM per node.

CPUs are dual Xeon E5645.

It would be more ideal if I could go with the 128GB option, but I don't want it to come at a huge performance cost... 

In this type of a situation, would the difference in the RAM clock speed produce noticeable performance gains or losses in a typical VM environment?

I could get away with the 96GB for at least 2 years.... So is the performance boost worth it?