Not sure what you mean, the benefits of separate browser profiles are huge and obvious - separate tracking for logins, sessions, etc. Before profiles came along my wife and I just used different browsers - otherwise we'd have spent all our time logging out of and back into facebook and twitter and so on. Profiles fixes that.

You can even make desktop shortcuts to launch Chrome with a given profile, so in practice it's like having two different apps. I guess you could launch one instance and swap users but we don't bother.