I'm not quite sure whether Seven News at 6pm would actually be the most watched news bulletin in NSW (at least not yet anyway) especially when these factors are taken into consideration...
In Sydney, Nine News is #1.
In Northern NSW, NBN News is an absolute ratings powerhouse (mainly due to Newcastle of course, but still).
Seven News Sydney does not air on weeknights in the Central West, Riverina, North West and North Coast regions because Prime7 runs their own 6.30pm "national" or "state" bulletin into those markets.
Yes, Seven News Sydney reaches more viewers than Nine News Sydney but I'm not sure you could say Mark Ferguson leads "New South Wales' #1 news" based on that alone.