Amazon Simple Storage Service (Amazon S3), provides developers and IT teams with secure, durable, highly-scalable object storage. Amazon S3 is easy to use, with a simple web services interface to store and retrieve any amount of data from anywhere on the web. With Amazon S3, you pay only for the storage you actually use. There is no minimum fee and no setup cost.
SFTP (or Secure File Transfer Protocol) is a network protocol that provides file access, file transfer, and file management functionalities over any reliable data stream.