I'm looking for a new Android phone to replace my current Nexus 5. It should be similar in size (the Nexus 5 is 137.8 by 69.2 mm, so a screen diagonal of about 5 inches) - I don't like the trend towards large phones. I am however looking for decent hardware. It should also come with an unmodified current version of Android, I also don't like waiting for months/years for updates as I had to in the past with a phone from LG. I'd prefer for it to have an audio jack and the navbar buttons on-screen, not as hardware buttons. Another thing bugging me about my Nexus 5 is that it only has 16 GB of storage - I need 32 GB at the very least.
I would suggest the 32GB model of the Motorola Moto G5
All Motorola phones come with as clean android as you are going to find on the market (compared to the Google Pixel) and they have very good hardware specifications, check in the link above.
Its screen size is 5 inches, the only hardware button is the home button, and it has an audio jack. Decent camera too.