Your questions are too generalized to give you any one answer. So much depends on the integrated amp.
For example, there are integrateds with very good preamp sections that can better some separates. And vise versa. While most preamp sections are active, there are some with passive preamps too. The Creek 5350 comes to mind. Finally there are a lot of power amps that cost way more than even a top class integrated.
So again, it all depends on the component being discussed. It would help to know why your are asking.