On Mars, metals are very abundant and easy to extract, and also minerals suitable for making glass or ceramic materials are abundant, but the raw materials for making food and organic materials, like plastics, are very scarce and expensive to concentrate.

On Venus, there are abundant resources for making organic materials and food (except for a few metallic bioelements required in small quantities, i.e. Fe, Zn, Mn, Cu, Mo, Co), but there are no resources for making metallic, vitreous or ceramic materials.

However, the materials that are missing on Venus are easier to transport from elsewhere, because they are required in smaller quantities and they are dense solids that occupy little volume. If not enough water would be found underground on Mars, that would be really difficult to transport from elsewhere.