The iPhone X camera upgrades are serious. The rear camera includes tons of new features that you will actually use including way better lighting for portraits that should help your photos look vastly better without the need to go buy a separate camera.
Apple now includes optical image stabilization on both of the rear cameras, to help with hand shake and to make your low light photos look way better. There is a new Quad LED true tone flash that offers better light uniformity so in the end your photos taken with flash will look better. Some of these features are also on the iPhone 8 Plus.
The real separation takes place when you look at the front of the iPhone X. Your selfies never had it so good. The iPhone X front facing camera includes Portrait Mode like the iPhone 7 Plus does to give you that super cool blurred background effect and you can also use the Portrait Lighting effects on the front facing camera of the iPhone X.