Model polymer composites of DNA wrapped single-wall carbon nanotubes (SWNTs) are used for a quantitative study of SWNT dispersion and alignment in stretched polymer films. By introducing a controlled deviation from ideal SWNT dispersion, we use small-angle neutron scattering (SANS) in combination with optical spectroscopy to establish quantitative relations between extinction, dispersion and alignment for SWNT samples that are enriched in both chirality and length. The effect of bundling and aggregation on optical absorption is assessed and the optical anisotropy of the dominant SWNT species is obtained and analyzed. We discuss the influence that polydispersity in length and chirality have on the optical response of these materials.