Hi Dashi,
No I'm not a GP, I'm a PhD physicist. That said both the central coast and the Pittwater are very nice places to eat. The central coast is about 90 mins from central Sydney and has beautiful beaches and cheaper houses (a new 4 bed will probably set you back around $500000, which sounds a lot but as a GP you'll probably be looking at $150000 per year or so? the one thing I missed about the central coast is a lack of restaurants and good cafes/bars etc. there are some but its slim pickings.
Pittwater however is even more beautiful, being a peninsula it has gorgeous beaches facing the sea for surf or swim, and pittwater beaches facing the inlet, which have no waves and are gently shelving for kids and families. There are more restaurants and bars (although not as many as UK) but Mona Vale is only 30 mins drive from Manly which has everything, and from there is 30 mins on a ferry into central Sydney.
So having lived in both, Northern beaches is where I would recommend. The central coast is still there for visits and holidays but I crave some night life and things to do, occasionally.
I hope this helps
Chris