I don't have a gzip benchmark for cssnano itself, but I know that the road to best compression is using both. http://stackoverflow.com/a/807161/1745309
Since v3.2.0 this is no longer done by default and can be enabled via the config object. The website should probably be updated to reflect this. https://github.com/ben-eb/cssnano/releases/tag/v3.2.0
I don't have a gzip benchmark for cssnano itself, but I know that the road to best compression is using both. http://stackoverflow.com/a/807161/1745309
Since v3.2.0 this is no longer done by default and can be enabled via the config object. The website should probably be updated to reflect this. https://github.com/ben-eb/cssnano/releases/tag/v3.2.0