afaik Jade can't be precompiled; all the parsing needs to happen in the Browser, whereas Handlebars (and therefore Emblem) can be precompiled so that browser processing is minimal. Also, for frameworks that heavily extend Handlebars, such as Ember.js, you'd miss out on a lot of features such as auto-updating templates if you didn't choose a language that compiled to Handlebars, i.e. Handlebars or Emblem.