Remember, a 9mm may slow down, but a .45 will never speed up
Lots of folks don't want to be pinched, doesn't mean I'd defend my home with a pair of pliers. :0 I wouldn't use this logic to select a HD gun.
I value in this order:
1. ability to shoot it well at speed
2. Tactics
3. penetration to a minimum optimal depth (14 inches?).
4. diameter of the hole.
(depending on how you define them, 1 and 2 may switch places)
That's to have the optimal chance. You don't have to have optimum to get the job done. Lots of folks accomplish HD (and hunting) with much less that the perfect firearm.
And for lots of folks the above is a .45
9mm certainly can help with #1, you can shoot more, and it is generally more controllable. Right bullet will help with #3.
I'm guessing you like the p7 as a platform, any reason not to increase the capacity and go with the p7m13?