Basically the workload that an average person is going to have: a bunch of processes running simultaneously with varying degrees of cpu and memory intensiveness.
In special cases you can get better performance with more, but less beefy cores (graphics is a prime example), but in general a few powerful cores performs better. The main reason is because communication among cores is hard and inefficient, so only embarrassingly parallel programs work well when divided among many cores. Plus the speedup you get from parallelize a program is minor in most cases. See Amdahl's law[1] for more on this topic.
Also, I'm not an expert in this area, but I have some familiarity with it. So hopefully someone with a bit more experience can come and confirm (or refute) what I've written.
