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Significant improvements have been made across the board, with Hyper-V now supporting increased cluster sizes, a significantly higher number of active virtual machines per host, and additionally, more advanced performance features such as in-guest Non-Uniform Memory Access (NUMA).

The tables below shows the improvement Microsoft has done with  Windows 20012 Hyper-V :

The table also shows that both Windows Server 2012 Hyper-V and vSphere 5.0 Enterprise Plus deliver up to 1TB of memory to an individual virtual machine, however, one aspect to bear in mind when creating virtual machines of this size, is the vRAM (Virtual Machine Memory) entitlement with vSphere 5.0.

• Each vSphere 5.0 Enterprise Plus CPU license comes with a vRAM entitlement of 96GB vRAM, and on a 2 CPU physical host, this would equate to 192GB vRAM added to a ‘vRAM Pool’
• The 1TB virtual machine would consume 96GB of the vRAM allocation (this is an upper limit established for an individual VM, and was one of the results of customer feedback around the original vRAM licensing announcements)
• This would leave only 96GB of vRAM for use by other virtual machines, restricting scale. The only option to overcome this would be for the customer to purchase additional vSphere 5.0 licenses at considerable expense. This is on top of the extra administrative overhead of monitoring and managing vRAM entitlements.

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