There is good to be said about slightly faster follow up shots with 9mm, I don't completely downplay that, but I also feel that focusing on that one single aspect where the 9mm shines has clouded peoples thinking. To me the "I carry a 9mm for faster follow up shots" mindset is not really applicable to real life.
It's not about "faster follow-up shots". It's about the
number of hits in the very short time available.
One more hit can mean the difference, in real life.
The .40 pokes bigger holes, expands larger, destroys more tissue, simply hits harder and does so in the same size package.
The most authoritative studies have concluded that, with today's premium defensive leads, the .40 is no more effective,
on a per round basis, in terms of wounding effectiveness than the 9, when it comes to human targets.
Keep in mind that there were significant improvements in bullet technology after the ,40 became popular.
Bullets do not wound by "hitting harder".
...shouldn't I care more about damage dealt to the target instead of how I perceive the recoil? With adrenaline pumping, nobody would notice the difference anyhow.
According to the FBI Training Academy at Quantico, there is no meaningful difference in damage to the human target--again, speaking on a per-round basis.
Perceived recoil might matter at the range, but
real recoil, as it affects the number of hits on the target in the same time interval, is important in defensive shooting.
The defender cannot decide what internal body parts to destroy and aim for them. The results depend on luck, and more hits provide more luck.