There's a gun store in my area that has a range and will let you shoot their rental guns. I'm probably going to go there and try a few out before I decide what I want to get.
That's the best way to go.
I don't agree that .40SW is a "one shot drop." Heck, even .45ACP isn't guaranteed to do that. Any caliber needs good shot placement . . . and with good (enough) shot placement, any caliber will kill. Sorry to use a semi-morbid example, but President Reagan came very close to dying from Hinckley's .22LR -- and that hit was a ricochet, but dangerously placed.
Using hollow-points, the differences between 40 and 9 narrow significantly.
If money is no object, going with the 40's greater power is an easy choice.
In a SHTF/TEOTWAWKI, the greater abundance of 9 might give it an edge.