The speakers are not historians of the genre or era, in fact three of the speakers are not historians.
John Julius Norwich is author of The Popes: a history (2011) an attempt to write a global portrait of the institution. According to Edward Pentin writing in the Catholic Herald, Norwich bases much of his understanding of Pius XII on Cornwall's "Hitler's Pope" (1999). This does not bode well for good and reliable history. Reviews of the book in the New York Times, The Guardian and Telegraph were generally positive, but point out that this is a general history not a detailed study of the whole papacy. Therefore, comments are likely to be more on the general side and indicative of the personal interests of the author.
Geoffrey Robinson, the well known human rights advocate who attempted to have Benedict XVI indicted for trial before the International Criminal Court in the Hague will also speak in favour of the motion. His book "The Case of the Pope" (2010) was given to me as a Christmas present by one of my students as a tongue-in-cheek end-of-school bit of fun. I read the book and while I admire Robinson's brilliance of mind and written word, I was not convinced of his arguments, spoiled as they are by a serious lack partiality and of understanding of Catholicism, the institution of the Church, the Vatican and Papacy. Catherine Pepinster, editor of The Tablet, wrote a balanced review of the work for The Telegraph. The review in The Guardian proves Pepinster's case, that a one-sided look will lead inevitably to a one-sided conclusion.
William Doino and Ronald Rychlak are two of the best known apologists for Pius XII. I have commented on their work several times on this blog. There is no need to re-visit their material here.
I doubt very much that this evening's debate will add anything of substance to the work historians are engaged in. In fact, I suspect that the only result will be a night of entertainment as two highly accomplished writers, Norwich and Robinson, neither of whom have much time for the Catholic Church, and less for Pius XII, will face two passionate and dogmatic apologists, Doino and Rychlak, who have shown in their writing little interest in the craft of history and great interest in propaganda and over-simplification of fact and contexts to further the agenda of various neo-conservative groups.
There may well be a few good laughs, but I doubt there will be much good history. Of course, I would be delighted to be proved wrong.