kerbarian said:The main differences are burst 5 instead of burst 2, and Cloudkill doesn't block LoS. It doesn't seem like much for going from level 5 to 19, but it is almost 5x the area covered.
Cloudkill moves slower... and can be more awkward to place, especially if you want to move it.
Side questions: is it clear whether moving a cloud into someone counts as them entering the cloud? If so, does the cloud actually move or does it teleport (a Stinking Cloud is small enough/moves fast enough to cross completely over someone in a move action)? How does Spell Accuracy work with movable zones (it looks to me like the specific squares you choose *at casting* are always omitted, it isn't clear whether they need to be in the initial area of the casting).