I would recommend getting whichever Shield presents itself first. If it is the 40, get that and a box of ammo. If later a 9 becomes available, you can always trade or sell the 40, and not lose a dime. If finances allow it, you could end up with both, like I have done. Then you have the glorious option of both. You could, at any time, sell either one. I have had nothing but reliable performance from both, by the way.