Both work very well. The AA#9 does well too. However, do not go on Speer's data for the AA#9 because it lists max as 14.6 grains. There is no way in hell you can fit 14.6 grains and seat the bullet. 14.6 would nearly overflow the case and compression would be out of this world. The load data for the Power Pistol was hard to find since Alliant only lists that powder with 147 grain projectiles. Here is a link with lots of info on the .357 SIG and lists Power Pistol for the 124/125 grain stuff. These are max loads listed and should start low and work up.

http://www.reloadammo.com/357sig.htm

Hodgdon's website lists Longshot for the 124/125 grain stuff as follows:

8.3 - 9.3 grains
OAL of 1.135"



Hope that helps.