I'm using a Dell Precision T7500 as a render cow node. The T7500 runs with xeon processors at 3.2 ghz and it is doing a great job at crunching out vue movie frames. I've noticed in the task manager that all cores work on the render tasks way up in the high 90 percent range so I think the more cpu cores you have the faster the image gets completed. Originally I tried 2 core 2 duo pcs running at 2.4 ghz and 1 I5 laptop.  Just the one T7500 curnches out more frames per hour than those 3 combined.

Also helps to have the render node connected to a fast network so you don't lose too much time in the long run as information is sent back and forth from the node to the render console pc.  Does not matter much for single pictures but when you render something like over 3,000 image frames with a slight delay of 5 seconds in transmission per image it adds up.