The eastern suburbs are "east" with respect to the centre of the city. The northern beaches are actually slightly further east, but do not rate as "eastern suburbs".
To put it in international terms, New Yorkers would probably prefer the eastern suburbs, while Californians would probably feel more at home in the northern beaches. South Africans prefer the leafy suburbs inland from the northern beaches, and the English look lost wherever they go, but the young tourists from urban Britain think Bondi in the eastern suburbs is just dandy.
The beaches, going south from South Head, are Bondi, Tamarama, Bronte, Clovelly, Coogee, Maroubra, with more beaches on the far side of Botany Bay.