If there are only 2 PC's or devices attached to a hub its as fast as a switch. If more than 2 are attached to a hub, they all have to share the available bandwidth. If use is light, there is no performance difference. If use is heavy (busy office network, servers & internet access & printing, etc.) performance can go down fast.
I don't know of any real benchmarks because the hub vs switch debate was pretty well decided before everything became popular on the internet but you can try a google search - maybe someone's paper was published.
Mike.