The units do matter.
If for example for the same boat
you use square yards of sail area for one ratio and square feet for another ratio, divided by the same units for weight, lets say US tons, the number will come out different.
Now if you take that same boat
and use square meters divided by metric tons, the resulting number will be different. Don't believe me? Try converting the sail area to square centimeters and see if you get the same number for the same boat.