Glenn Fleishman picked Google over Apple.
iCloud Photos is a fantastic way to sync your images and videos across all the devices you own that use the same Apple ID for iCloud, have access anywhere via a web browser to the same media at iCloud.com, and let Apple effectively perform a backup (or extra backup, depending on your configuration) of all your media.
I use both, but prefer not to give all my iCloud photos to Google so they can make money from my photos. The differences between the two are obvious.
Instead of being device-centric with a cloud-based sync part, Google Photos—like many Google products—is cloud focused, allowing you access, download, or sync data on devices or via Google’s web apps. With Google Drive for macOS and Google Photos for iOS and iPadOS, you can automatically sync images you import to specified folders.
Apple is privacy-oriented, while Google wants you to share so they can make money from your photos and from your friends and family members.