Category talk:Informal arguments

How to decide what goes in Category:Arguments versus Category:Informal arguments?
I was looking at the contents of Category:Arguments versus Category:Informal arguments, and I have difficulty imagining the criteria that were used to sort pages into one category or the other. There are pages in each category that could as easily go in the other category. What criteria should be used to decide what goes in Category:Arguments versus Category:Informal arguments? Thanks, Biogeographist (talk) 16:45, 3 January 2019 (UTC)