Don’t let anyone justify that there is a difference between the two. They are the same. Our language is strange. Saying either of those is acceptable but I think that most people say, “get dressed.” Other examples of this kind of thing are that the word read can be pronounced as “reed” which would be used in present or future tense while it can also be pronounced “red” as past tense. There are probably thousands of examples of this kind of thing, 20 or so that are very common. Our language is far from perfect…it’s even far from being as close to perfect as most other languages.

Dress means perform the action of putting on clothes. Get Dressed means do whatever you have to do to become a person with clothes on.

The terms are interchangeable, depending on which sounds most natural in the context being used.