Those looking for a powerful flagship smartphone with a great camera built with the top components and materials will want a Nexus 6P. Smartphones with high-quality cameras with near-SLR quality have been built before, but not at the Nexus 6P's $500 entry price. Nexus phones are a good choice because this category of Android phones get regular software updates directly from Google.
The non-removable battery has been a dealbreaker for me, but with 80% charge in 20 min and doze mode, it might be a non-issue in the short term. It will still be an issue long-term when the battery starts to wear down, though.