If it was as simple as what is the weight difference between an equal amount of steel, brass and aluminum, you could use this weight calculator and obtain the values.

http://www.principalmetals.com/utilities/primecalculator.htm

In real life there are probably more variables. Could you obtain actual weights either online or by phone for each of your possible choices?



"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson