I've been doing several configurations on the R710 that will be used in a Hyper-V cluster.

I like the idea of having the 72GB Memory (18x4GB), 800MHz Dual Ranked RDIMMs option for the price point for the overall cost of the R710, but had concerns using the lower memory speed for the virtual machines.  To be in the same price point for 1066/1333, I would have to settle for the 48GB option.  Obviously, 48GB is better than what we currently have (32GB 2950's), but was looking to walk the fine line of best performance/price/max number of VM's per node.

Any advice/thoughts on memory specs for R710 and virtualization?