The Nighthawk although very good will only work if it can find some sort of mobile signal which sadly is missing in much of outback Australia. Also it is often dependent on what carrier you are using Telstra, Optus, etc. Where as The Starlink satellite system should work just about anywhere you can see the sky, It depends on how far off the beaten track you intend going and how imperative it is that you have internet access.
Landy

The advantage of the Nighthawk is partly its supposedly better internal antennas, plus the ability to plug in external antennas, particularly MIMO ones. But as Landy said, you need some sort of signal.

The ongoing cost of Starlink is less if you can survive on the $80 / 50Gb plan. The Australian Starlink Users FB group has a tips and tricks document about how to redice your data usage to improve your chances of not exceeding that limit. Some people can manage on it, but you mentioned streaming and that is likely to blow that plan.

We bit the bullet some months ago and have rooftop 12v Starlink. Never looked back. Smart TV, can the Sat dish, can the foxtel and Vast box. Excellent. $3k installed and operational.