Pretty nice at this small size! IMO, even side-by-side at up to maybe 11x14 or even 16x20 the phones are getting better and better as the traditional camera makers seem to simply iterate small improvements...
In the last year I updated my SE to X to XS and now a 12 and shooting sometimes side-by-size with my Z6. During the lockdowns, it was one nice diversion that kept my creativity from withering.
My recent week on the road to SoCal and the Colorado and Mojave deserts, I had more fun with my iPhone 12 than with my Z6 though I have a full collection of both modern and vintage (1950s-1960s Leica) lenses.
The spontaneity shooting with the 12 and having all the tools in a box that fits in my pocket was priceless and enjoyable! Yet being able to get a larger file, shoot vintage lenses also has its merits. But then, there's the cumbersome post on the Z6, captions and metadata, spotting the skies, especially small aperture/wide angel lenses...
This trip, I used the Z6 like I was shooting film and left the processing/post until I got home versus having a blast in situ with the iPhone and playing with the images in the which was a lot like shooting an SX-70 and manipulating the prints while still wet.
The iPhone is becoming another useful tool in the field for more than just a fast snap...it's fast to share the images (AirDrop, FB, Instagram, texting and email) and a lot of fun and useful for sketching before making the commitment to the "real" camera, if I even decide to do so.
No matter what, they both take good craft to create a great image. Images with the iPhone are capable of remarkable prints, some even quite large and even before the "enhanced resolution" that for some images works great and others not so nice.
The writing is on the wall and I hope I can make it through the next big shake-out and keep up on the bleeding edge and making new work.