N011 vs N011M Radar

First, please clear up this confusion for me. Is N011 and Zhuk-27 the same radar?
According to this article http://www.ausairpower.net/APA-Flanker-Radars.html
the newer N011M actually has lower Peak Power compare to the older N011. Why is that? N011M has a what has been described hybrid ESA antenna. What are the operational advantages of N011M over N011?

thanks