Welcome aboard cocco...
I don't fish Winthrop (or the North Shore too much for that matter) but I'd say the water to your north is superior depending on access... There are many points and sections of beach and rock that are littered with more rocks and boulders in through Swampscott and Marblehead that are likely to hold fish. Much of that structure you see where the shore meets the water continue beyond the surfline and that structure holds fish...
Here's a random pick of Swampscott to give you an idea:
The actual site is here:
http://coast.mit.edu/mb_index.html