The Sigma still wins in the corners, but chromatic aberrations are largely absent for both lenses.
With new photographers, I often try to get them to take a 50mm f/1.8 through its paces early in their careers. One of the key milestones in the proposed shot-list is a series of images at f/8. It is eye-opening to see an inexpensive lens deliver top-notch results on even the least-expensive cameras. Beginners are often drawn to the selective depth of field of the wide aperture primes, but to me, the greatest joy of these timeless (and lightweight) double-gauss designs is their ability to render superlative quality at their diffraction-limited apertures.
