Sony FE 14mm f/1.8 GM ($1,598) and Sigma 14mm f/1.8 DG HSM Art ($1,599) both offer excellent optical performance, but Sony GM is better corrected for sagittal lens flare resulting in cleaner astrophotography images. Sony GM also offers much smoother bokeh due to use of two XA (eXtreme Aspherical) elements.
Sony FE 14mm f/1.8 GM weighs in at just 37% the weight of the massive 2.7 lb Sigma 14mm f/1.8 DG HSM Art.Sony FE 14mm f/1.8 GM is less than 2/3 the length of Sigma 14mm f/1.8 DG HSM Art.
Thanks to its nearly silent XD Linear AF motors, the Sony FE 14mm f/1.8 GM offers much faster and quieter autofocus than Sigma’s rotational stepping motors.
Sony FE 14mm f/1.8 GM has a de-clickable aperture ring. Sigma does not.
Best of all, the Sony FE 14mm f/1.8 GM actually costs a buck less than the Sigma behemoth.