resistance is all about cross-sectional area of the cable

Sort of correct but stranded cable has more surface area for the electrons to flow on - so it has benefits of being lighter, flexible and stronger and it will carry the same amp rating as solid piece of wire of the same gauge and material - that applies to pretty much to low voltage dc and ac circuits.

There are some new copper clad aluminum cables that are much lighter than copper for main feeds - I am not sure how well they perform in the long term as usually aluminum and copper together eventually corrode and get brittle