Yep, they're both pretty comparable in their API surface, and more general purpose than Apple Geo Anchors, as neither are tightly coupled with GPS. Rather you create an anchor and then save it to the cloud. On your own you can tie it to a GPS location if you'd like. Though Azure Spatial Anchors does have more functionality than Google Cloud Anchors (Coarse Relocalization + find nearby anchors in the anchor graph).
- Apple Geo Anchors (iOS & not all locations so not ready for use yet) [3]
Integration with these SDKs is pretty easy, and Azure Spatial Anchors and Google Cloud Anchors are production-ready. Minecraft Earth for example used Azure Spatial Anchors for shared multiplayer AR experiences. Infopop is nice, but doesn't have multiplayer or long-term persistence, so not really useful as-is. But wouldn't be surprised if it eventually uses one of these SDKs to provide better multiplayer + shared relocalization. You could probably throw together a rough version of Infopop in a week if sufficiently motivated, ARKit does a lot of the heavy lifting there.