Neither is "better". They are each fine in their own right.
my opinion is the 45 ACP round has more knock down powder then the 40 caliber
Yes, a 45 caliber bullet is bigger than a 40 caliber bullet. A .45 is0.45 inches wide in diameter and a .40 is 0.4 inches in diameter.
@ .05 inches
No
Either platform can be larger than the other. The 45 has the larger projectile. Caliber is defined as the diameter in fractions of an inch, so .40 caliber is smaller in diameter than .45 caliber. Caliber can also be defined in the metric system, measured in milimeters. The .40 caliber cartridge is equivalent to 10mm in diameter. As noted, the size of a handgun can vary widely within one caliber, so it is perfectly reasonable to have a smaller handgun crafted in a larger caliber.
45 has the larger projectile. Size of the handgun will vary.
.40 Smith & Wesson is a 10x22mm cartridge, whereas the .45 ACP would measure 11.65x23 in metric measurements. The .45 is a larger round, and also a much slower round.
If you are talking about a PCP (PreCharged Pneumatic) rifle. With a .45 caliber pellet, then "Yes" It can. I don't believe there is a 40 Caliber pellet gun.
There are various difference, but the most common answer would be the .45 is .05 of an inch larger in diameter than a .40.
45
Assuming the question is in regard to firearms and ammunition, you can read the "caliber" of a round as a decimal how wide the bullet is in inches. So a .40 caliber round is .4 inches wide, or about 10.16 millimeters wide. A .45 caliber round would be .45", so a little bit fatter than the .40 caliber round. The caliber doesn't tell the whole story of a round though, it doesn't say how long the bullet is, how heavy, how big the casing behind the round is, how much kinetic energy is hits with, etc. The .40 S&W round has an average of 425 ft/lbs of energy right at the muzzle, while the .45 ACP, a "bigger" round, has about 400 ft/lbs.
Vary from .22, .25, .30, .40, .355, .45