When we say that copper is a heavier metal than aluminium, we are comparing their densities. In a similar way, when we say that copper is a better conductor than aluminium, we are comparing their resistivities.
Density and resistivity are both bulk properties of a material. Their value doesn't depend on the size or shape of a particular sample only on the material itself.
Resistivity: depends on the material only
Resistance: depends on size and shape - as well as on the material.