Against the slightly shorter, faster $299 Sony E 50mm (75mm equivalent) f/1.8 the Sigma is noticeably sharper, and vignetting is low. In spite of the faster maximum aperture, however, the Sony has excellent control of Chromatic Aberration though and achieves a similar Image Quality rating overall. Given the faster aperture and OSS (stabilization feature), the Sony is a good choice even though it’s more expensive. For all that, the Sigma is excellent value.
Comparing the Sigma MFT mount lens with the best performing telephoto prime available for the Olympus/Panasonic cameras we can see that the modest little 60mm is not to be ignored. Given the $700 price difference, the Sigma is outclassed in many ways and yet could still be a contender. Over the comparable aperture range (f/2.8- f/22), the Sigma isn’t far behind in sharpness levels and there are no real shortcomings elsewhere.