VMware Machine CPU Configuration sweet spot (Server 2012 / 2008 R2)

VMware Machine CPU Configuration sweet spot (Server 2012 / 2008 R2)

Let's assume I had enough free ressources to allocate in my VMware vSphere
5.1 Landscape.
Can anyone point me to an optimal CPU Configuration (Number of virtual
sockets / number of cores per socket) in regard of the sweet spot.
Where does allocating more sockets and cores not benefit the VM anymore?
Also, does this sweet spot vary between a Windows 2012 and a 2008 R2
Server? Assume I am talking just about the OS performance, not the
performance of any possible applications running on the server.
Thank you for your inputs.
Riscie