The correct comparison is:
The stems and the roots are both transportation systems, moving different things the plant needs. However, the roots actually get water and essential nutrients out of the soil, while the stems just deliver these things to where they are needed.
In this comparison, it's important to clarify that the roots absorb water and nutrients from the soil, while the stems transport water (and nutrients) from the roots to the leaves and other parts of the plant. Additionally, stems also transport the products of photosynthesis (like sugars) from the leaves to other parts of the plant.