slim

Rails allows you to choose your own testing framework [1][2][3] and plugins[4][5][6], templating engine[7][8][9], and ORM[10]. It's my understanding that before Rails 3, swapping out many default Rails was a bit hacky, but it's pretty standard now. [1]: https://github.com/rspec/rspec-rails [2]: https://github.com/cucumber/cucumber-rails [3]: https://github.com/thoughtbot/shoulda [4]: https://github.com/thoughtbot/factory_girl [5]: https://github.com/nulldb/nulldb [6]: https://github.com/notahat/machinist [7]: https://github.com/haml/haml [8]: https://github.com/josh/mustache-rails [9]: https://github.com/stonean/slim [10]: https://github.com/brasten/sequel-rails [11]: https://github.com/datamapper/dm-rails [12]: http://mongomapper.com/documentation/getting-started/rails.h...

https://github.com/stonean/slim#benchmarks Slim is mentioned in the writeup. It's faster than Haml. I like it better.

Slim defaults to ugly-mode: https://github.com/stonean/slim/blob/ae14457c596c963144810ce... Haml uses pretty-mode in development and ugly-mode in production.

One of the biggest reasons to switch is that Slim supports streaming and Haml doesn't, or at least won't until the next major version. Sources: https://github.com/stonean/slim#slim, https://github.com/haml/haml/issues/436

It's called Haml and Slim, not HAML and SLIM. Are you running the server in production mode? Slim already has a set of benchmarks that compares it to Haml and ERB in various settings: https://github.com/stonean/slim#benchmarks Do all three template engines use automatic HTML escaping?