- Has http://learnboost.github.io/stylus/ been considered? I've heard that
it's a good compromise between sass and less (but I haven't played with it myself to see if it really lets you do more compass-like things).
I was just writing a message about Stylus [0] so I'm glad you brought it up. Limn [1] uses Stylus and we've been pretty happy with it. I read the RFC carefully and it seems the two big reasons to pick LESS over Stylus/SASS are popularity and support in PHP. The reason to pick Stylus/SASS over LESS is a more elegant syntax and a slight edge in features.
*PHP support* - Stylus does have PHP support [2] but it's not even close to as mature as the LESS support.
*Popularity* - does matter; one of the long comment threads on the RFC is from a potential contributor who is concerned that LESS makes it harder to contribute. I mostly agree with Jon's and Steven's arguments that LESS is pretty easy to learn. However, I have also heard about a year's worth of complaints about Limn being written in Coco instead of pure Javascript. I personally think CSS -> LESS is just as mentally taxing as Javascript -> Coco, but I'm objectively in the minority based on the feedback I've received. I'd be cautious here. You can upcompile CSS into LESS, sure, but if a contributor has to understand a complex LESS codebase full of mixins and abstractions while debugging the generated CSS in the browser, they're right to point out that this requires effort. And this is effort is only increased for more elegant languages like Stylus.
*Syntax* - Stylus and SASS definitely have cleaner, simpler syntax. Stylus aims to be the cleanest of the three but it definitely smells like that SNL skit about the number of razor blades. They have 4 blades?! Fine, we'll make one with *5* BLADES!!! What I'm referring to here is that Stylus has optional colons and tries to be as much like python as possible.
*Features* - The interesting thing about the features comparisons out there is that all of them seem to be outdated. For example this write-up [3] highlights that @media queries can be nested in SASS (same is true for Stylus). But the LESS people implemented that as well (Feb 2013). This said, it does seem that Stylus and SASS are leading the pack in terms of new features. Introspection [4] is a very cool one in Stylus that I'm not sure you can do in LESS.
I think the decision's pretty much been made to go with LESS, and I agree with it. I think it strikes the better balance between making it easy for people to contribute and DRY-ing up our codebase. But in the future, if we loved the migration to LESS and we just wish it had more features and more DRY-ness, we should revisit Stylus.
[0] - http://learnboost.github.io/stylus/ [1] - https://github.com/wikimedia/limn/tree/develop/css [2] - https://github.com/AustP/Stylus.php [3] - http://css-tricks.com/sass-vs-less/ [4] - http://learnboost.github.io/stylus/docs/introspection.html