Yes, You can use Swift service also. Both of them provides almost similar features for storing, managing highly scalable object storage system. I do not see many differences between them except Swift is open source.
Both has scalable proxy mechanisms to forward the request for object GET/POST /DELETE/PUT. Hash functions are used to store the objects on nodes in swift. S3 is also using the hashing to encrypt the location and may be using the advance options for security.
In S3 objects are stored in Buckets. Swift follows Account→container→object.
Rings, zones, partitions features are also available in S3. The open-ness of Swift has made it is really easy to understand it, rather than S3 for which we know only how to use it.
Hope this will help you.