Hi Fabien,
I arrived 5 months ago in Sydney and have experienced several places, Balmoral, Botany bay, Foreshore road, Kurnell, Palm beach, and looking forward to check other places, especially for waveriding.
It is funny because I am french and live in Neutral bay ;-)As far as I have seen I can tell you the following:
Summer= mostly NE wind starting round 12am when it is sunny = slalom in Balmoral. No big winds 15knots (I have 130lts/7.2 m) but sometimes it work everyday!!!
Balmoral is my favorite because so close (15mn!) and beautiful. Water is warm, sun is shining...What else?!!!Winter= W winds, gusty, the worse direction because land wind. There are several options including Foreshore road (Botany bay), La Perouse, little Manly and more.
It is still good to be able to windsurf though.For waveriding, you need more volume (90l) and bigger sails than in France. You get bigger waves but fewer wind. Sydney has more slalom conditions to offer.
The link Stehsegler provided is relevant...I can't wait NNE to test waves at Wanda!
nswwavesailing.org/spot-guide/One thing you should consider is that you have to pay for (expensive) car park almost everywhere here, even in remote places.
Parking is a serious matter here...No kidding.
Anyway you'll have plenty of options and beautiful scenery, enjoying speed and wind! Kind of a paradise!
I'll be happy to show you some spots.Jean-Marc