Sam2:
R’ Schachter was actually who I quoted about it above. His actual lashon, which I have heard him say several times, was “the Mishnah Berurah changed the halacha on every page”.
And his main critique of the AH is that his Mehalach through the Sugyos is very often Mechudash and against Rishonim.
Well the Aruch Hashulchan was probably following R’ Shachter’s position of “[p]asken[ing] by whoever is right”. And presumably he was Higia L’hora’ah.
R’ Schachter actually tells a good story which illustrates the need to know all of Shas when paskening any issue: Back in his youth, he was learning a sugya with his chavrusa (I think it was something in Yevamos) and they decided that after they learn the sugya really well they would take out an Igros Moshe and read a ???? relating to their sugya, and without reading R’ Moshe’s answer, they would “pasken” the ????. So they did it, and they came out with a different psak than R’ Moshe. Why? Because R’ Moshe brought in a Gemara (I think in Bechoros) which they had never heard of. That’s the basic gist of the story – I might have gotten some details off since it’s been a while since I heard it.