subs v. replace v. xreplace - help needed on a minimal viable example of their difference

[Conrad Schiff]

All,

  I am trying to understand the actual differences between the 'subs', 'replace', and 'xreplace'.  I've reviewed the documentation (some of it seems stale) and various discussions in this group.  Perhaps I've missed something but I've not found a side-by-side minimal viable example of that shows when to pick amongst these.

  Does such a thing exist?  If it doesn't is there any interest in making such a thing.  I would be happy to take the first draft of documenting this if (and only if) I can get help from the rest of the group.

Thank you,

Conrad Schiff, PhD

Professor of Physics

Capitol Technology University