If you asked about PostCSS-based preprocessors (it is small part of PostCSS features) — there is a 2 solutions:

* postcss-cssnext, preset of CSS drafts polyfills. It is not 100% preprocessor, but because of CSS custom properties and CSS nested polyfill it could do preprocessor work. * PreCSS, preset of PostCSS plugins with Sass-like features.

I use PreCSS. It is more simple preprocessor. It has no some Sass features by design, to keep your code clean of code.

Using PreCSS doesn’t give me some addition features, just same old $style variables, nesting, mixins.

The reason why I use PreCSS — performance and compatibility. If you use Autoprefixer or Stylelint, you already have PostCSS in your build processor. In this case, why you should use other parser? PreCSS will share parsing with Autoprefixer, Stylelint and other PostCSS tools.

PostCSS will parse CSS only once and all that plugins will work on top of same AST. As result build process will be simpler and faster.