The Nest Hello doorbell has long been the doorbell for Google/Nest users. But it comes at a high cost of entry, including a sometimes difficult installation process. That’s where the new Nest Doorbell (battery) comes in. It’s almost as good as the Nest Hello, but simplifies installation and brings the cost down.
Source: Nest Doorbell (Battery) Review: The Doorbell for Every Google User? – Review Geek