One "Faster" server slower than the other
You are running in a virtualized environment so just because a server has more virtual RAM or more vCPU's doesn't mean it's "faster" (as you call it).

Several factors are abstracted by the virtualization layer and you would need to know and even benchmark them all.

For example, there is no guarantee the storage underneath the vmdk's is anywhere near comparable, so you would need to benchmark the storage and monitor it on a physical level. 

The underlying physical CPU's could make a huge difference too. How fast are the physical processors? Are the CPU's overcommitted in the virtualization layer (i.e. are more vCPU's assigned per physical core) etc.
You could look at the CSTP or RDY values in VMWare among other things.

It really isn't possible to call one server faster than another because it has more virtual resources if you don't know the underlying hardware and virtualization configuration.

Some things you could check are


Storage performance
vCPU/pCPU ratio (overcommitting resources)
The vm's running on the same box (you might not know what your neighbour is doing unless you get access to the VMWare/Hyper-V counters such as esxtop CSTP and RDY values).
NUMA setup on the VM layer
power settings and hyperthreading configuration in the bios of the underlying machines to make sure they perform well when not fully stressed (like they are when running benchmarks)
...


I hope some of these pointers can help you troubleshoot further, but without any hard evidence about the underlying hardware there really isn't any point in comparing the virtual resource configuration to determine which VM should be "faster"

That being said, you may get some mileage looking at perfmon counters to determine disk latency or cpu load, or even use some VMWare counters such as effective speed in MHz or stolen time and you could get some information from wait stats but I still think getting access to some information about the VM configuration and underlying hardware is essential.  

If you can, benchmark the underlying hardware.