The best scenario is having a large number of fast CPUs in your system. However, in many cases you must choose between having multiple, slower CPUs, or a single, faster CPU. The benefit of fast CPUs is that they run single-threaded operations very quickly, for example end-of-day processing such as applying all of your payments prior to running your general ledger trial balance. On the other hand, multiple CPUs allow you to do two different operations simultaneously, for example one user can be entering orders while another is shipping products. This has obvious benefits to the business in terms of efficiency.
The best way to decide is by looking at your options and your application to determine. For example, an application that does a significant amount of single-threaded operations will benefit from a design that has fast CPUs, even at the expense of having fewer total CPUs in the system. An application that is mostly data entry will benefit from a design that has more CPUs, even at the expense of each CPU being slower. This is another case where having knowledge of your application and workload allows you to make intelligent system decisions.
