For what it’s worth, I still think Motorola’s Moto G lineup produces the best android phones under $300. They’ve really focused on battery life. They even have a model with a 5000mAh battery.
The new entrant to this space is the Pixel 3a, which starts at $399. Had the 3a been around when I was looking for an upgrade, I think I would have picked it over my Pixel 3. Some commentary about the 3a below: