1) the NATURE of the documents -- Here, the PRA governs and clearly states documents subject to the PRA are all agency originated documents, working papers, drafts, etc. that are shared with the Administration AS WELL AS personal notes, logs, diaries maintained by the President. As far as the PRA is concerned, the word "mine" doesn't exist when it comes to Presidential records. The only applicable word is "ours" as in the National Archives. Note that the applicability of the PRA has nothing to do with the security classification of the material. Even documents related to the planning and execution of the yearly Easter Egg roll on the South Lawn are covered by the PRA.

Sure. But the PRA excludes "personal records" from the definition of presidential records. If something is a personal record, it's not a presidential record. Trump is arguing that these decisions are not reviewable. He is not basing the argument on any claim that the documents meet the criteria of "personal records" under 44 USC 2201. He's instead arguing that the matter is not properly before the court, and that no review is possible.

This is a thin reed. However, Trump's attorneys have some prior examples of where courts have declined to wade into the details over whether past Presidents have gotten it right when designating records as "personal" or "presidential." So they argue that the entire question is not within the court's purview.

I don't think their examples are particularly strong, so their argument is probably wrong. But it's important to recognize what their argument is. They're not claiming that these documents actually meet the statutory definition of "personal records," but that once the President has said they are, a court cannot review that determination.

documentcloud.org - Trumps motion to dismiss the indictment based on the presidential records act