Which pot is bigger?

As I was making braised beef short ribs for dinner the other night, I was faced with the question of which piece of cookware to use - the rectangular lasagna pan (in the shape of a rectangular cube) or the circular Dutch oven (in the shape of a cylinder)? Or did it even matter? I wanted to use the piece of cookware with the largest volume possible since I had a lot of short ribs and wanted to cover them completely with broth. Without using specific numbers, how would I go about finding out which piece of cookware has the largest volume?