There are many handgun/shotgun powders that are better for low pressure cartridges like .38 Spl and .44 Spl, than AA9. Almost any of them as a matter of fact. Pick just about any propellent in the Unique/HS-5/Universal/WSF burning range or faster and they will all work well and efficiently. If you use a slow powder like AA9 you will need much more to get the same performance as any listed above will give.

In other words, SteveC is right on with his answer and rational.