As to charts and studies......I have my own theory based on first hand observation. I have seen people in third world countries that never saw a movie and didn't know they were supposed to fall down and die. They kept fighting till their blood loss to the brain didn't let em continue.
Also I have seen a trend in victims that makes me think that past experiences and trama to the body helps one react to shock and trama better. Ie; if you were raised by a parent that never struck you, didn't partake in contact sports or had any brothers to fight with as a child you will not handle the trama of a injury very well.
On the other hand , if your old man abused ya by beating your ass three times a day , had 4 or five older brothers or friends that liked to wrestle , play full contact football ect ect then your more than likely going to handle trama to your body better.
As a deputy sheriff I saw shooting victims die from all calibers, the speed of their demise was not directly based on the size of the caliber either. One more key item to consider is that if the kinetic energy does not stay within the cavity of the body then the effectiveness of the round, large or small is lost IMHO. That is what makes the .45 ACP such a great round. The advent of modern hollowpoint designs such as the .45 ACP Federal hydra shok and the slower velocities 750 -900 FPS make it a very effective man stopper if armed only with a handgun. The permanent wound cavity versus a temporary wound cavity seems to be a key consideration also. My second choice in caliber is as yours, the .44 special , my choice of brand is the CCI 200 grain Gold Dot Hollow Point.
Bottom line is that if I have to use deadly force I want a 12 gauge shotgun loaded with slugs and #4 buck backed up with a transition sidearm in .45 ACP if I have the time and choice. If not , the first rule is to have a firearm......, second rule is if you can't hit your target under stress or not , your caliber, ability to handle recoil and training needs to be seriously reconsidered.
Just my two cents on the issue ........Stay Safe !