Is his "writing style" disputatious? No, Franklin is generally not considered controversial in his writing style. In fact, he fits right in with both Realism and Neoclassicism if you ask me. It is very "eighteenth century" so-to-speak. Let me explain. Ben Franklin rightly called his The Autobiography of Benjamin Franklin simply his "Memoirs," although he never officially titled them as such. Franklin's own description fits the work rather well.
The style is mostly narrative in nature, with Franklin telling amusing anecdotes about his trial and error as a young lad trying to become a great writer. Most notably, I remember one part of the work with Franklin revealing the story of himself pushing around a wheelbarrow full of papers in order only to "appear" industrious, ... when not doing so in reality. He wanted others to "see" him pushing around a wheelbarrow full of paper in order for them to say, "Oh my, look at that industrious lad, ... what amazing work he must be doing." Ha!
I suppose it is odd in the fact that the style blends from a more informal tone to a more formal one, ... becoming more didactic in nature as the work progresses. However, this is the nature of a memoir, eh? I love how Franklin's work depicts one of the original concepts of "The American Dream" where a young scamp, through the appearance of industriousness, can advance in society and social standing in order to become a success.