we familiarly say one body is bigger than another; but it sounds harsh (and I think is never used) to say one matter is bigger than another.
Guk maiz esaten dugu gorputz bat beste bat baino handiagoa dela, baina belarrira gaizki jotzen du (eta uste dut sekula ez dela erabiltzen) materia bat beste bat baino handiagoa dela entzuteak.