Be aware that all of the 3 allowed specs have quite different global purities, and G11.1 has something like 4 QVL's, ranging from pretty good argon to stupid good argon. 17.1 does not seem to specify which QVL you can/should use if you select G11.1.
That being said, what base metal will you be working with. If you are into some Ti, look into higher purities