No.
$489!!
45 has the larger projectile. Size of the handgun will vary.
Yes
Generally, no. The .40 caliber is usually a very large handgun and very heavy/ hard to conceal. It CAN be done, but not easily unless you are a very big person or wear a coat all of the time.
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.
it is a little less powerful but not by much
It all depends on you, your pocketbook, your skills.
100-500 USD depending on EXACTLY what 40 caliber mode you have.
A 40mm handgun would fire a bullet the size of a golf ball. No such critter. There IS a .40 caliber handgun (about 10mm). There are dozens of larger caliber handguns than .40 caliber. They include the .41, .44. .45, .455. .460, .475, .500- and several others.
In the United States, each department sets its own requirements for what officers carry. In the city where I live, officers carry Sig 229s. In the county, officers carry Sig 226s. In another city near me, officers carry Glocks. In yet another city, officers carry H&Ks. All of those I mentioned, carry .40 S&W caliber. All that said, however, Glock is the most common.
The model 19 is a 9mm only proposition. The model 19 is not available in .40 caliber, but the model 23 is the same size gun and it is a .40 caliber gun. Some people would say that the model 23 is the .40 caliber version of the model 19.