I'd like to get some advice on what factors influence the decision of how large (in terms of resources) you would decide to size each node of a virtual machine cluster (VMware, Xen, etc), and in what way. What are the benefits/drawbacks of multiple smaller individual nodes (less cores, RAM, etc) vs. a smaller number of larger individual nodes? Is there a balance to be struck, and if so, in your experience, what do you consider when attempting to find the optimum?
I appreciate that there almost certainly isn't a one size fits all answer to the question, but what factors would you take into consideration?