I've used scss and less and I prefer SCSS.<p>When I first started using less I found the javascript parser missing some functionality that was in the full ruby gem. Also, since I use django, I found integrating with scss much easier, especially with pyscss.<p>I find that scss provides a level of abstraction that I am comfortable with. Because of pyscss I can run it from the command line and figure out exactly what is going on pretty easily.<p>With compass I find that I write much cleaner css code. But the big win is being able to nest my css. Nesting CSS brings it much closer to the HTML that you are styling.<p>In my mind this is the huge win.
Last time I checked, Stylus provides more powerful abstractions and a cleaner syntax<p><a href="http://learnboost.github.com/stylus/" rel="nofollow">http://learnboost.github.com/stylus/</a>
I won't use LESS CSS for anything. Why? Because it's another layer of abstraction which is a pain in the arse to debug when it goes wrong, which it does regularly. It's ok for about 3 months which is enough to build some false confidence in it, then WHAM problems.
I got bit by the switch from Ruby to Node.js. The Node.js arrangement was considerably more difficult to set up on the older systems we maintain. Most annoyingly lesscss.org makes no mention of the switch away from Ruby. Our plan right now is to abandon less-css and just check the converted CSS into our repo - the (server setup complexity) costs far outweighed the benefits.<p>[edit]
Well I guess the old repo did mention the switch :\ <a href="https://github.com/cloudhead/less" rel="nofollow">https://github.com/cloudhead/less</a> still frustrating
I had been thinking about using LESS/SASS for a new project, but ultimately I decided on PHP. Overkill perhaps, but it gives me access to the rest of the site variables, database calls, etc.