Topsiders / beach Blanket buffet = organized line to get your food
cabanas = madhouse -where are all the food choices? ... Oh here in this line, and over there in that line, and it looks like there might be something else over there, and what's this line, oops, same stuff as one of the other lines I was in --- hey where did you get that? Oh, that line over there. Why should I wait, I can just crowd in here ....
Frankly my opinion of "cabanas style" is it's a stupid mess! It's not a great way to move a lot of people through.
On the other hand, the "single line" method on the classic ships doesn't work when there's a "long line" and the people at the back decide that they need to save a table for their family because "there are so many people in font of us" -- when that happens, the people that have been through the line, and have their food, have to search for a place to sit and eat, blocking the next groups of people from coming through. So you end up with people standing with trays of food, and another group of people sitting at the tables without food (waiting for their family to bring them food, but can't) so you get gridlock.