Sass Mixins vs Extends: The Data - Belly Card Engineering

The debate between using mixins or extends in Sass has been heating up recently. From the surface it appears they both provide solid benefits in helping us write consistent and modular code. However, the critics are out and extends specifically have come under fire. But why?

Interesting results: Although mixins create more code than extends, the gzipped CSS is smaller and somewhat faster to evaluate for current browsers.