Answer :
I would say roman numerals because they look more sophisticated, but I don't think it should matter.
Answer:
With Roman numerals
Explanation:
An outline should be made as a "preparation" of the official speech, so it should be written in a formal, clear and coherent language. In addition, the outline should be separated into sections to facilitate the division of the subject into parts and categories that allow the discourse to be more organized. When you divide your speech into categories you will realize that you have divided the categories into topic and subtopic, in which case using the example shown in the question "claim" is a topic and "introduction" and "supporting details" are subtopics, just as "counterclaim" is a topic and "supporting details" and "refuted points" are its subtopics.
The topics of a document should always be numbered with Roman numerals, so we can state that claim and counterclaim should be labeled using Roman numerals.