What storage provider should I use?
It is seeming more and more that Cloudflare R2 is the best option for most users. With its S3 compatible API, it is easy to migrate existing data and integrate into your existing setup.
What are other considerations when choosing between storage providers?
You may want to consider the usage pattern of your own application. For example, if your app is constantly reading and writing to S3 you may get a better performance with S3 as Cloudflare R2 requests will require reaching outside of the AWS network.