Did you ever think about how much fabric was in a Jelly Roll vs. a Layer Cake? Which one give you more fabric? They are exactly the same!
2 1/2" X 40" X 40 pieces = 4,000 Square Inches
10" x 10" x 40 pieces = 4,000 Square Inches
In terms of body shape, I wish I was more like a jelly roll (long and skinny), but in reality, I am more layer cake shaped
Since they are the same amount of fabric, It is best to evaluate the pattern you want to use and determine which will give you the least amount of scrap.