I'd like to attempt a post analysing the differences between the Aruch Hashulchan and Mishna Berurah. Before I start on that I will try to sketch a brief intellectual profile of these two Great leaders.
The Chafetz Chaim's is well known for his extraordinary piety, integrity and humility. The Chafetz Chaim was a Tsaddik in every sense of the word. It is important to emphasize that all of the CC's work is generally focused on the masses. With the exception of his Mishna Berurah, the vast majority of the CC's books are geared towards the masses. They are written in an clear and simple fashion, Devarim Ha'Yotzim Min HaLev V'Nichnosim L'Lev, exhorting the common person towards good deeds and proper behaviour.
Certainly, even those books that that are of a popular character show tremendous erudition but it is important to emphasize that the Chafetz Chaim’s greatest effort was to reach even those who were not great scholars. He wrote works for woman, for soldiers and for all those who were in need of Chizzuk. The Chafetz Chaim cared deeply about the common person. I am not aware of any teshuvos, or in fact of virtually any work of a purely scholarly character.
The Chafetz Chaim was not an intellectual. There are numerous letters of his exhorting people not to read the literature of the Haskalah . He could not understand why anyone would want to read a newspaper even a “kosher” one. (See his son’s description in Sichos CC). His son recounts that at one point he picked up a book by one of the great Chassidic masters and after scanning it briefly, he said “I do not see anything here that I need. The words of the Tannoim and Amoraim contain all that is necessary.” He was against the study of philosophy of any sort (“the philosophizers”. His son writes that when he was younger he started reading the Moreh Nevuchim. His father was unhappy with this and took the book away saying, “if one needs to read this sort of book it shows that the emunah is not well-founded”.
His attitude towards the Chassidim seems to have been very mixed. Although he appreciated their role as the defenders of the faith, he did not consider Chassidism to be the correct path. He said that on the left are the philosophizers, the right the Chassidim, and the middle path is the way of true belief, the way of the Mishna and Gemara. (See sichos for more on this.)
The Chafetz Chaim believed very strongly in the Kabbalah. His son recounts that, on occasion, late at night his father would study Kabbalah (see Sichos for a list of Kabbalah Seforim that the CC owned) but he was sad that he did not have the time to study it seriously.
 I would imagine that the shiurim he gave in his Yeshiva were of the same clearness and simplicity that characterizes his other works.
 See Chaim Grades description of the problem of forbidden literature in “The Yeshiva”. Interestingly, the story of the destruction of the library is also mentioned in Meir Einei Yisroel, although the hero is the CC not the CI(?).