|JoelF847 RPG Superstar 2008 Top 32, 2011 Top 16|
The difference is that with stinking cloud, once you run out of the cloud (generally on your next action), you only have to deal with it for 1d4+1 rounds (avg 3.5), while glitterdust can last many, many rounds at 1 round/level. Plus, in stinking cloud, while you're in it, you have 50% concealment, so that first round when you lose your action you actually have decent protection due to the spell.
Also, stinking cloud is 3rd level vs. 2nd level, so it should have some advantages...
You can still fight while blind, though; there's basically nothing you can do while nauseated except slowly run away. And the duration for Stinking Cloud is just as long as the duration for Glitterdust while you're in the cloud.
I guess my point is that when I hear people talking about powerful spells, Stinking Cloud is usually up there with Glitterdust and Evard's Black Tentacles.