The update to the pagination tutorial includes a bit broader scope of functionality - mainly allowing for pagination from database results and how to be sure you're not dropping any additional query string variables included in the script (always a good thing).

The Ajax tutorial goes through just the basics - how to create and make the connection to a background PHP script. They also give a more "real world" example than just a "hello world", a script that can handle two types of requests, one of which is a call to a database to return results back to the script.