Attached Link: http://www.renderosity.com/viewed.ez?galleryid=682410&Start=1&Artist=haloedrain&ByArtist=Yes

Volumetric slabs can look good, but render times can be much higher and it's harder to control exactly where the clouds are (as in, the densest parts of the volumetric slabs). It also takes a lot of tweaking to keep them from looking weird as they go off into infinity, although with the angle in cornelp's image that wouldn't be a problem.