Nice sum up of the various possibilities indeed.

A remark: though I understand you had to keep each section brief because you wanted to cover all topics, I think you could have emphasized a little more on the use of xquery over the openrowset method, as xquery is mostly far superior in performance and memory use over the openrowset method. I found that most articles on the sql & xml subject tend to first list the 'outdated' methods and only after that get to the newer, easier methods. This results in many people giving up reading before they have actually gotten to the part where the easier methods are described. Your's is no exception, sadly.

Then, why is the section on converting attributes into elements included in your article? I've got 2 reasons for this question:

1 - the solution shown does not use SQL server to solve the problem, nor can it be automated, so it is often not usable for your target audience, sql server admins/developers, and

2 - SQL server processes data from attributes a lot faster than it processes elements. Even though I do agree that many xml documents use attributes for the wrong purposes (but that is for different reasons), if the document already has its data in attributes, then why not take advantage of this fact and have SQL server process the data from the attributes directly instead of doing all the pre-processing to convert them into elements and then have a bigger document that processes slower?

And a tip: You don't need an external tool to 'tidy' xml data: formatting xml data can easily be done from SSMS: While inside an opened xml document window, the 'Edit' menu contains the 'advanced' -> 'Format document (Ctrl-K, Ctrl-D)' option. This formats the entire xml document, also an option to format just the selected text is available.

A second tip: to put xml output by SSMS into a file many people copy from the Results tab and paste the xml text into some other editor, to save it from there. It is far more easy to right-click the column header (output into grid must be on for this, but that is required for almost anything when working with xml) and select 'Save Results As...'. In the file dialog that opens, first change 'Save as type' from the default 'CSV (Comma delimited)' into 'All files', then enter a file name (including the .xml extension) and press Save. This works well for much larger result files than can be copied using copy-paste.