That's exactly the case with the pre-aspheric 'lux, you nailed it to a tee. This is the reason Leica enthusiasts use to carry both the 'lux and 'cron. One for people, reportage and low light, the other for landscapes or work requiring edge to edge sharpness especially at wider apertures. The C-Sonnar/Planar combo is a different kettle of fish in that the C-Sonnar doesn't perform as well as the pre-asph. 'lux wide open while the Planar is quite similar to the 'cron. However, both have better flare supression than their Leica counterparts.