In VMware ESXi 5.x, does it make a difference if I select 2 CPU cores vs. 2 CPU sockets?

Solution 1:

No, your VM should perform the same and will use the same resources on the host. It's just a design choice which was primarily added to add some flexibility where your OS or software may have per CPU licensing requirements.

Each socket / core will represent one physical core on the host. Remember that more cores isn't automatically a good thing due to the scheduling requirements.

Solution 2:

The main purpose of the cores/socket option is to provide flexibility with software that may have runtime or licensing requirements based on the number of "physical" sockets or CPU cores.

While there's no difference in performance between multiple cores on one socket versus a combination of multiple sockets, there IS a slight difference in operation if you enable or require the CPU hot-add feature of the virtual machine.

With the VMware CPU hot-add feature, you can add a socket to a running VM, but not additional cores. As odd as it seems, this is something I run into in production at work, and has influenced how I configure new VM's.