If you go by just the energy numbers, the 9x19 has more energy than the .38 Special. However, compare the numbers of a 9x19 and a .45 ACP with the same barrel length. I would choose a .45 ACP for personal protection over a 9x19 or even a .40 S&W. Actual performance is more important than paper numbers. I have talked with farmers and ranchers who have both 9x19 and .38 Special, and they say the .38 Special performs better on problem wild animals. It is rare a second shot is need with the .38 Special, but it is normal for two or three shots to be required when shooting a 9x19 on the same type of wild animal.

You mentioned your wife has a SP101 in .357 Mag. Does she have the 3" barrel or a shorter barrel? You lose velocity and energy with every inch of barrel length while gaining muzzle blast and muzzle flash. I prefer the medium power .357 Mag personal protection ammo with a heavier bullet in 3" barrels. It is a good idea to shoot your personal protection ammo in a controlled environment in very low light to see how much muzzle flash your ammo produces in that particular firearm.

Here is a link that has some interesting info.
http://www.ballisticsbytheinch.com/