Wait For a More Durable Phone
The Pixel 3a and eventually the Pixel 4a obviously caters to a crowd that doesn't want to spend $900 on a smartphone, but that's not the only thing to consider.
This phone will deliver almost the same experience as the Pixel 4 does but cost under $500. You'll get a great screen, smooth Android 10, be the first to try the Android R beta, and the cameras will be awesome. Not to mention all the Google Assistant stuff.
Perhaps the biggest and best reason to wait for the Pixel 4a is that it'll be a more durable phone than the Pixel 4. In order to make it more affordable, Google made the entire Pixel 3a out of plastic, instead of a premium aluminum frame and glass on the back. And while those materials look good and feel premium, they're fragile. I don't think any smartphone should have a glass back. It's just one more thing that breaks too easily.
If you're tough on phones and don't want to spend $900 only to probably break the glass on the front or the back, wait for the Pixel 4a. It'll be more rugged, more durable, more capable of surviving a drop or two, and it won't cost $1,000 either. As you can see from the video here by JerryRigEverything, the Pixel 3a can handle quite a bit of abuse that the glass Pixel 4 couldn't.
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