You're comparing some apples and oranges here (maybe even a banana?) Sass is a language, where as the others are frameworks. Compass is a SASS (and SCSS) engin

You're comparing some apples and oranges here (maybe even a banana?) Sass is a language, where as the others are frameworks. Compass is a SASS (and SCSS) engine that provides SASS-based frameworks such as Blueprint, which I noticed you didn't mention. To answer your question though, I swear by Compass+SASS+Blueprint+HAML. SASS => CSS, HAML => ERM/HTML, Blueprint is the framework, and Compass ties them together. The biggest reason in using Compass+Blueprint is semantic layout selectors, with mixins to define Blueprint grid widths. Instead of <div class="span-16"> you can use .left-column, and then add a SASS mixin to tell left-column how many columns to use. This takes the content from presentation methodology a step further, which the grid system has always violated somewhat.