Should I use @import or manifest files?

Rails 3.1 introduces a new way of organizing both JS and CSS with the introduction of manifest files. For example, application.js might look like this:

//= require jquery
//= require jquery-ui
//= require jquery_ujs
//= require_tree .

This will grab various bits of Jquery, all of your own JS, concatenate them together and serve it as a single file to clients. Simple enough.

Unfortunately the picture is not so clear to me with SASS. SASS already has concatenation built in using @import.

Should I change all of my partials into full SASS files and then concatenate them using the manifest file or continue using @import? Why?