Look, 9 out of 10 attackers dont make you hit them.
Then over half stop after being hit solidly, once in the chest, even with pipsqueak loads like 380 jhp's, 9mm ball, and 38 lrn. So it's a very, very small fraction of attackers who require any sort of real "stopping". All the longarm does, short of shtf, is get in the way, and be too slow to access and use. The 10mmm is plenty as a manstopper. the problem lies with getting the hits. reloading 10mm costs very little more than reloading the 9mm.
In fact, if you practice with a lw,compact 9mm, and carry a full size and wt 10mm, the adrenalin dump of combat will preclude your having any detectable diff in performance. Pistol defense is nearly always at 10 ft or less, you know. It's usually not used against a gun, either. The reason the handgun sucks against autorifles is lack of effective range. Beyond 10 yds, the handgun sucks in combat, just like a rifle sucks beyond 100 yds, when you are being shot at.