I agree... 40 cal is much better than 38 or 9mm. It's also very easy to handle.
A shotgun loaded with birdshot is great for home defense... you aren't going to put holes in your neighbors.
I've got to give 38+p's their props though. I used to live three miles into the national forrest... literally 3 miles from the nearest road. All the girls that lived in the cabins up there carried light alloy 38 hammerless snubbies loaded with 38+p's. It is absolutely the perfect ladies' gun if you get the Lady Smith J frame.
And in the forrest... all the girls kept their shotguns loaded with OO buckshot. We had some truly stand up women on that mountain.