The 9 Pro is the top model and will go on sale later this month for $1,199 (£829, or about AU$1,480).
The base OnePlus 9 meanwhile will start at $729 (£629).
I love the 9 Pro's design. It's classy and sophisticated, with an all glass and metal design that feels luxurious to hold.
There are neat shiny accents around the camera unit and it gives the whole phone a definite feeling of elegance that wouldn't be out of place in a nice cocktail bar on on the table in a business meeting.
The OnePlus 9 Pro's 6.7-inch display has a 3,220x1,440-pixel resolution, while the base 9's measures in at 6.55-inches with a 2,440x1,080-pixel resolution. In all honesty I can't tell the difference in resolutions so don't let that put you off opting for the cheaper model.
Inside, both phones pack Qualcomm's Snapdragon 888 chip, which supports 5G data speeds and is an absolute powerhouse. There was nothing I could throw at either phone that would slow it down.
The 9 Pro has four cameras: a regular zoom with a larger image sensor, a super-wide lens, a 3x optical telephoto lens and a smaller monochrome lens on the bottom.
Shots are decent, but there's room for improvement.
It's disappointing, as OnePlus's cameras have always been the weak link in its phones and the company's recent partnership with professional camera manufacturer Hasselblad promised great things, which so far hasn't paid off.
The back is a fingerprint magnet. Keep a cleaning cloth handy.
The OnePlus 9 ditches the the 3x optical zoom lens and uses a smaller image sensor in its main camera.
Its images are decent, considering the more affordable price of the phone, but they're not in the same league as phones like the Galaxy S21 Ultra or iPhone 12 Pro Max.
In short, if imaging is critical for you, then look elsewhere.
Both the OnePlus 9 and OnePlus 9 Pro support 65W fast charging which will take the phones from empty to fully charged in around 30 minutes.
It's lightning fast and makes it great for giving your phone a quick boost in the afternoon. That's more important on the 9 Pro, in fact, as its battery life is not nearly as good as the standard 9's.
Both phones have fingerprint scanners built into the displays.
The OnePlus 9's display curves attractively at the edges. It's one of the little elements that makes this phone feel like the more premium of the two. Which it is.
My review model OnePlus 9 Pro had 12GB of RAM, although that will vary by region.
Both phones run Android 11 at their heart, but both also have OnePlus's Oxygen OS over the top. I like this software as it's neat and easy to use and doesn't seem to slow the phone down over time.
There are a variety of camera modes to choose from.
The OnePlus 9's purple tones look great.
The 9 Pro's maximum screen resolution can be dialled back a touch, which should help eke out some more battery life.
Mirrored phones are a nightmare to photograph. Just saying.
The screens on both phones fill the whole front of the device.