They're all pretty much the same, unless you're looking for specific use cases, e.g. camera, outdoors ruggedness, gaming, specific OS build, etc. I stopped getting flagships once I realized my old ones battery started to swell like a cheaper phone. I'm on Android, so I get to replace any app with the one of my choice - I'm particular about data submissions to home and sneaky stuff like autotagging. Now all I look for is a recent android build (for app compatibility), decent camera hardware (I'll replace the app), IP68 and a good price.
Privacy reasons. Didn't like the autotagging in the default app on my oneplus. Turns out it's a common feature on all the new phones now. I now use procam x. Bear in mind, using a third party app means you lose the advanced filters and processing the manufacturers have spent money developing. Some of the camera hardware will also not be accessible. I don't really care since I also have dedicated hardware for beauty shots.