Measuring cups or scale - which is better?

I almost always use my digital scale to measure food - peanut butter, cereal, rice, whatever it is. I have found that with shredded cheese, for instance, it's almost impossible to measure out 1/2 cup accurately because of all the space in between the shreds, etc.

My question is....which is more accurate in relation to how they design the nutrition labels? When they figure out nutrition facts, are they measuring by weight or by using something similar to measuring cups? The reason I ask is because I have found a huge discrepancy in the number of servings they allege on the label and the number I get in the package when I measure.

For instance, Uncle Ben's Ready Rice comes in a pouch that says 2.5 servings per pouch (I think). Each serving is 1 cup each. If I use a measuring cup, there is absolutely no way in hell I can get 2 1/2 cups out of that pouch. Maybe 2 cups tops.

I want to make sure I'm counting and measuring accurately.