We have several "pizza bracha" questions on this site, but, I will focus on a specific item on this answer. Excerpts:
1.The opinion of Harav Moshe Feinstein zt”l holds two slices makes you responsible to wash.(I believe this would be the Main Psak (Halachic Ruling) for American's)
I'm thinking that at the time Rav Moshe said this, he was referring to the "standard" dough thickness and the standard pie diameter which, according to Wikipedia is 14 in. in diameter. (I am terrible at trigonometry, so, I don't know how to calculate that into what the volume of 2 triangles would be.) There weren't too many kosher pizza stores in the NY area and, from my recollection, NY style pizza was the only style available.
Now, kosher pizza stores sell different pizza styles. Besides Sicilian (answer to that is addressed in the linked answer), there is thin crust, Chicago pan pizza (thick crust) and probably a few other styles I can't think of. The pizza pies also come in different sizes.
Given all these options, my question, here, is has anyone compiled a revised ruling regarding how much one can eat (assuming following the rulings that distinguish amounts between "snack" vs. a meal. I know there are rulings that don't make this distinction.) before he would be required to wash and say "hamotzi" that addresses the various pizza styles? Obviously, all this is related to the volume of dough that's consumed, but, has anyone related these styles to the "triangle" concept ("piece") as above?