Ring Video Doorbell (1st Gen) has sensors on the back of the device and a mounting plate. Ring Video Doorbell (2nd Gen) does not have sensors on the back of the device or the mounting plate. To get the mount off the doorbell, put two fingers on the mount.

Video Doorbell (2nd Generation) has 1080p HD video (vs 720p HD on the original Ring Video Doorbell), an additional near motion zone that provides motion detection in areas only 5 to 15cm in front of your home, and a revamped mounting setup that simplifies installation and removal for battery charging.