you can look at the mass dedicated to each sense I suppose and use that as a proxy, occipital lobe vs temporal lobe. Couldn't land a search hit on those quickly though.

Just from a signal processing perspective, sound is a 1D data type, though we do have stereo sound and can localize sounds, so that's some additional processing there I suppose. There's also frequencies involved. Image processing is typically more demanding than audio from what I understand with computational things, images being 2D, or 3D sources. This is a pretty interesting exploration relative sensory input load.