Answer by Tyson for XML-RPC vs REST

REST vs RPC implementations like XML-RPC is a false dichotomy. You can implement a RESTful interface using XML-RPC (although you probably wouldn't want to). That said, there are a bunch of reasons why you would want to expose resources in a RESTful way using vanilla HTTP instead of rolling your own RPC interface using a technology like XML-RPC:

1. Future actions are primarily controlled by the server instead of hard-coded in the client via procedure calls, simplifying deployment and versioning.
2. Existing implementations for things like caching, throttling, and versioning can be used out of the box.
3. The custom procedures that you roll with an RPC interface are likely to be too narrowly scoped.

See this blog post for more info.