In practical terms the penalty for recoil in operational use is increased shot to shot recovery time.
For example If I need to shoot two or three opponents I can do so faster with 9mm than with the .40.
When I was considering switching from issued 40 cal P229 To POW G17 I ran Bill drills, the FAST, body armor / failure drills and some multiple target drills with the 229 in 40, the same gun with a 9mm conversion barrel, and a G22 and G17. The timer doesn’t lie.
Different guns have different recoil impulses. Recoil spring strength and polymer frame material type makes a difference. While the HK and the Glock are both “plastic” guns the Glock polymer is softer and flexes more that the HK polymer. You can actually fell the difference in recoil between the Gen4 Glock 22 and earlier Gen.
Memory can lie. For 8 years I carried an issued HK USP Compact LEM .40 cal with our issued 155 grain ammunition. At the time it was “normal.” However after years of shooting 9mm Glocks and 180 grain 40 out of an all metal P229, I shot 200 rounds of our old 155 grain through my personal HK USPC. It was not like I remembered and was kind of unpleasant to shoot. The gun and ammo didn’t change, but I did. The real test would be to put it on a timer with an identical 9mm.
During agency testing our national armory staff graphed the pressure curve of various duty loads. Basically, if you look at the pressure graph of a .45 it looks like a low hill, as the pressure is not only lower but spread out over a longer period of time. The 9mm looks like a classic “bell curve” while the .40 and .357 SIG graphs look like a spike on an EKG.
Todd Louis Green, the late founder of PF wrote an excellent article on why “Feelings lie.”
https://pistol-training.com/archives/5108