Closure stylesheets have one feature that no other framework has--minification.

If you view source on a lot of google sites you'll see that style class names are obfuscated.

The one caveat is that you need a sophisticated build system to pull this off (though it's easier if you use the other closure tools).

I was going to argue that Compass has :compressed output, but halfway thru, I realized you're right.

However, the beauty of Compass is that it doesn't rely on being intrinsically tied to the HTML it affects, whereas Closure stylesheets do.

All things considered, I'll stick to Compass/SASS.

I guess if you already used one or more of the Closure Tools, you might want to use Closure Stylesheets over Sass, even if Sass was slightly better.