Wow. This is a philosophical question actually. If the philosophy is to ensure consistent documents across multiple users, then a template (a real one) is a no-brainer.

Using a document to copy then modify for use has an inherent In-stability. As you noted, it can be affected by different Normals; it can also be affected by whatever the heck anyone wants to do with it. Using a real template increases the chance of consistent documents dramatically. So. If you want consistent documents, use template and styles.

That being said...good luck with that. This is a philosophical point that extends back decades really. I tried for years and years to get our users to use templates, and much more importantly, trying to get management to insist on it.

You have to have buy in from those who can insist on using a template. And at least some sort of training to demonstrate to users that it works in their best interest to use them.

Charles was actually more concise: templates create other documents, documents do not. So if you want to create documents, use a template.