Depends upon what you set out to measure.
lbs is specifically a unit of force.
kg is specifically a unit of mass. It is a category error to equate these as measures, although (in many places) an everyday convention to do so
on Earth.
IIRC the English unit for mass is the slug. If the tecnical limit is 70lbs or so, that is must technically be read as lbs force -- aka force of gravity which varies with location.
