Sass vs Stylus vs LESS

less.less

.border-radius (@radius) {
  -webkit-border-radius: @radius;
  -o-border-radius: @radius;
  -moz-border-radius: @radius;
  -ms-border-radius: @radius;
  border-radius: @radius;
}

.user-list {
  // need to use special `.` syntax
  .border-radius(10px);
}

sass.sass

@mixin border-radius($radius)
  -webkit-border-radius: $radius
  -o-border-radius: $radius
  -moz-border-radius: $radius
  -ms-border-radius: $radius
  border-radius: $radius

.user-list
  // need to use special `@` syntax
  @include border-radius(10px)

stylus.styl

// This and all CSS3 funcs are included in `nib` stylus plugin.
border-radius()
  -webkit-border-radius: arguments
  -o-border-radius: arguments
  -moz-border-radius: arguments
  -ms-border-radius: arguments
  border-radius: arguments

.user-list
  border-radius: 10px


// or

.user-list {
  border-radius: 10px;
}

I was about to decide on Stylus becasue the mixins are simple to write and since i already know Sass. But now after JunTheProgrammer comment i am worried to use stylus or go with Sass only

@JunTheProgrammer, it's only CSS ultimately, though. Do we really need endless repeated articles on how to write a mixin? The Stylus documentation has everything you need.

It's worth noting that Stylus is no longer in development at the time of writing. The last commit was on July 18th, 2016 (https://github.com/stylus/stylus). SASS/SCSS is still under active development with the last commit made 5 days ago at the time of writing (https://github.com/sass/sass). At this point in time SASS/SCSS has feature parity with Sylus if not more. In this situation I am more willing to develop using a technology still being updated over a project which has not seen an update in almost a year. I don't buy the excuse that Stylus is no longer being updated because it is feature complete either.

@Shirasho - Stylus seems to already be perfect - so, whether you buy it or not - you'll just have to try writing a project in Stylus - and then the same project in SCSS - and you will never use SCSS again. Unless you really like writing @import hundreds of times...