Q: Which is heavier, an ounce of gold or an ounce of lead?
A: Gold. Precious metal weights are measured in troy ounces, and a troy ounce at 480 grains weighs more than an avoirdupois ounce at 437.5 grains.

Q: Which is heavier, a pound of gold or a pound of lead?
A: Lead. There are 16 avoirdupois ounces in an avoirdupois pound but only twelve troy ounces in a troy pound.

I'll stick to metric, thank you very much!