This is a list of air gun pistol platforms, to compare them for use as Firearms Training Aids
Airsoft
Shotting 6mm plastic BBs these guns can use CO2, Green Gas, Spring or Electric power. Most models are generally made for Airsoft game play and not for use as a firearms Replicas with the exception of the some Glocks and 1911s. Good for use indoors and out.
Pros:
Ammo is Inexpensive
Ammo is Biodegradable
Can be used for Force on Force Training
Highest Variety of Power sources
Light weight ammo, Lower power, Less Destructive
"Safest" of the Platforms
Cons:
Lower number of Replica Models
Light weight ammo, Low power, Low Accuracy
BBs
Not to be confused with the 6mm Plastic Air Soft BBs. These shoot .177 or 4.5mm Steel BBs. These are more commonly found in CO2 and Spring powered
Pros:
Both the Guns and Ammo are Inexpensive
Highest number of Replica Models including the most compact concealed carry models.
More accurate than Air Soft and Paintball
Depending on the BB Trap Ammo is Reusable
Cons:
Solid Backstop and specified BB Trap recommended
NOT for use as Force on Force Training
Pellet
These guns shoot a lead pellet in .177,.22,.25,.30,....,.50 cal. Most pistol models are .177 cal. They are the dirtiest of the platforms in regards to clean up. Also available in CO2 and Spring though I don't know of any Spring Replicas. With a solid lead projectile, higher power, and rifled barrel these are the most accurate of the platforms.
Pros:
Large number of Replicas
Higher Power
Higher Accuracy
Cons:
Not recommended for Indoor use
Lead Ammo
Least "Safe" of the platforms
Solid Backstop and specified Trap recommended
NOT for use for Force on Force Training
Paintball
This is the newest addition to the list, BUT they don't just Shoot Paint. In .43, .50, and .68 cal they can use Paint, Rubber, Weighted Rubber, Nylon, Chalk, Powder, and Pepper (like burn your eyes pepper, aka OC) Powered by CO2. More often referred to as Mag Fed Paintball. There are very few companies is this market.
Pros:
Made for Force on Force Training (Paint only)
High Variety of Ammo
Some of these guns are marketed for Home Defense and Personal Defense (see Less Lethal)
Rubber and Plastic Ammo is Reusable
Cons:
Replica models are right now Limited to common Military and Law Enforcement Duty Arms
Most are not very accurate beyond 25 feet