In pistol, what are the advantages of cal. 40 over the cal. 45?

well since you didn't say what pistol was going to be used by each magazine capacity is not an issue , 40 cal is a faster traveling round that still has very good stopping power. 45 caliber is a slower traveling round with massive stopping power due to the slower speed and bigger size . a faster bullet will most times travel through the target before it has a chance to expand fully. Prices on the different calibers are not that much different but the 40 has become the more commonly used caliber second only to a 9mm at least in law enforcement.

Ammunition is smaller, which means you can fit a couple of extra rounds in each magazine, and lighter, which means those extra rounds don't add too much more weight to the loaded weapon.

And, as already stated, the ammunition is very slightly cheaper.

40 will go a bit faster and farther. the gun may hold more bullets depends on the gun. 45 is more common and cheaper to shoot

less recoil, smaller cartridge so you can fit more ammo in the same size pistol

btw. that is a 40 in my pic.

Less recoil and depending on gun type, size of shooters hand they are a little easier to handle.

Cheaper bullets.

One can shoot your foot off. the other one, you ***. Try cherry bomb instead.