I want the bad guy down and out NOW.
Unless you shoot them in the head, that will not happen unless they fall down voluntarily because they realize that they have been shot and are hoping that if they fall down you will not shoot them anymore and call an ambulance. The vast majority of shootings end because someone realizes that they have been shot and surrender by falling down.
Other than good shot placement, the most reliable means of stopping someone as quickly as possible in a home defense situation(ranges less than 25yrds) is to use a 12-gauge shotgun with full power 00-Buck shot(preferable copper plated). It is the equivalent of being shot 9 times with a .32 caliber pistol in terms of how much stuff it damages with every shot.
Whether you pick .40S&W or .45acp should be more based on the characteristics of the platform. Most .40S&W pistols fit the hand better, have more manageable size, and better magazine capacity. The .45acp makes a larger hole overall in the body, but the .40S&W shoots through barriers such as windshields and car doors better. Using heavier bullets the recoil feels very similar.......40S&W 180gr, and .45acp 230gr. Middle weight bullets such as the 9mm 124gr, .40S&W 155gr or 165gr, and .45acp 200gr tend to generate the most felt recoil. Given equal pistol weight and grip dimensions, a 9mm 124gr+P will feel more snappy than a .45acp 230gr, and a .40S&W 155gr will feel more snappy than a .45acp 230gr. However, if you use 9mm 147gr, .40S&W 180gr, and .45acp 230gr they are all pretty manageable with the 9mm being more controllable than the .40S&W, and the .40S&W being more controllable than the .45acp(once again, given equal pistol weights and grip dimensions). I generally prefer the .40S&W for duty carry and the 9mm for off duty carry with heavier bullet weights.
FBI Test Protocol:
Bare Gelatin = covered with T-shirt, Shot at 10ft
Denim = 4 layers shot at 10ft
Heavy Clothing = shot at 10ft
Steel = 2 pieces of 20 gauge, shot at 10ft
Wallboard = 2 pieces of 1/2" gypsum board, shot at 10ft
Plywood = 1 piece of 3/4" AA fir plywood, shot at 10ft
Automobile Glass = 1 piece of 1/4" laminated safety glass set at a 45 degree angle with an offset of 15 degrees, shot at 10ft
9mm 147gr(990fps): (Penetration/Expansion)
Bare Gel: 13.9”/.65”
Through Denim: 14.5”/.66”
Through Heavy Cloth: 14”/.66”
Through Wallboard: 15”/.67”
Through Plywood: 14.8”/.62”
Through Steel: 17”/.45”
Through Auto Glass: 10.8”/.52”
.40S&W 180gr(990fps): (Penetration/Expansion)
Bare Gel: 13.8”/.67”
Through Denim: 14.3”/.70”
Through Heavy Cloth: 13.4”/.64”
Through Wallboard: 13.1”/.66”
Through Plywood: 15.1”/.64”
Through Steel: 17”/.52”
Through Auto Glass: 12”/.61”
.45acp 230gr(905fps): (Penetration/Expansion)
Bare Gel: 11.6”/.75”
Through Denim: 12.7”/.72”
Through Heavy Cloth: 12.3”/.75”
Through Wallboard: 15.2”/.69”
Through Plywood: 18”/.453”
Through Steel: 16.5”/.53”
Through Auto Glass: 12”/.58”