Basics
Pistols are not used as main weapons. They are side arms that are quicker to use then fully reloading your primary weapon. Some pistols have high damage, some have low. Some have large ammo capacity, while others have half of the highest capacity. All pistols have their pros and cons. It is up to you to decide which pistol you wish to use.
There are four different types of pistols. The M9 and USP .45 are the pistols you start off with. The M1911 .45 and the Desert Eagle are unlocked later.
M9-
Accuracy: Rather low
Damage: Low
Range: Like all pistols, low
Ammo: 15 in clip, 30 spare rounds
Recoil: Low
The M9 is a very weak gun. The only upside to this gun is that it has the largest ammo capacity. If you want to kill someone with this gun, you must hit them multiple times do to its lack of "punch". I would not recommend a silencer since the gun is very weak as it stands, the silencer will make it even weaker.
USP .45
Accuracy: Rather low
Damage: Medium
Range: Like all pistols, low
Ammo: 10 in clip, 20 spare rounds
Recoil: Low
The USP .45 uses the same ammo as the M9. It is stronger then the M9, and just as accurate. When using this gun, don't go trigger happy like the M9 as it is quite a bit stronger. I would suggest silencing this gun as it only makes it a little weaker, and it does not show up on other player's radar.
M1911 .45 (Unlock at level 16, Gunnery Sergeant)
Accuracy: Rather low
Damage: Medium (little more the USP .45)
Range: Like all pistols, low
Ammo: 8 and 24 spare rounds
Recoil: Lowest of all pistols
The M1911 is like the USP except it hits a little harder, has less recoil, and has less ammo. Personally I prefer this gun over the USP, but it is really up to the player. Silencers can be used with this gun effectivally.
Desert Eagle (Level 43 Brigadier General, Gold plating at level 55 Commander)
Accuracy: Medium low, best of all pistols
Damage: Highest of all pistols
Range: Like all pistols, low
Ammo: 7 and 14 spare rounds, lowest of all pistols
Recoil: Pretty high recoil, highest of all pistols
There are many mixed feelings about the desert eagle. It is very powerful, but it has a high level of recoil and not much ammunition. Personally, the desert eagle is my favourite pistol. At level 55, a gold plated version of this gun is unlocked.
My Preferences
My favourite gun is the gold plated desert eagle. It looks nice and packs a heck of a punch. It is good when you run out of ammo because it does not take long to kill your enemy. If I wish to go for stealth on say the map, "Wet Works", I will not use the desert eagle as it cannot be silenced. I have found that the easiest and most efficient way to use the desert eagle is to aim at the upper or lower torso and fire fast, but not crazy like the M9.
Again this is my personal preference and in no way am I saying that this is the best gun, you may find that it is the worst for you. This guide should help you to decide on which is the best pistol to use. Try all of them and then decide.
Thanks for reading.