Is it better to create a taxonomy term using the 'create' method of the base Entity class or the entity storage manager?
In procedural code it doesn't matter, because both do the same. The static create() is a shortcut for the second example. (The different result is because the first saves the term and the second does not, if you want the term as result then save in a separate step)

In OOP code a better way is dependency injection. The second example points in the right direction. Inject the entity type manager, store it in a class property and use it:

$term = $this-&gt;entityTypeManager-&gt;getStorage('taxonomy_term')-&gt;create($term);


How to inject a service depends on which class you want to use it in.

A lot of base classes include services already and if you are lucky such a common service like this is one of them. Sometimes, for example in a controller, there is a method to retrieve the service. Then add to the code above parentheses: 

$term = $this-&gt;entityTypeManager()-&gt;getStorage('taxonomy_term')-&gt;create($term);


See ControllerBase::entityTypeManager().