All three typeshave their merits.
CO2 is usefull for fast repeat shots (ie: Big Crosmans, QB78, Sheridan). These rifles have adequate hunting power out to 30 yds.
Springers, have more refinements, and in some models velocitys of up to 1200 fps in .177. The .20, .22, and .25's have tremendous knockdown power for hunting.
Pneumatcs. The better grades of Crosman (old and new) are powerfull, The Benjamin/Sheridans in the bigger calibers have been a mainstay of american airgun hunters for decades, the .177 Benjamin is high velocity (near to 800fps) and has it's varied applications.
Best model of any gun , is the one that you are proficent with, and this takes time and pratice. Small game has small vital kill zones. NO need to wound or mame game or varmits, and doom them to a torturious and agonising death.
Make your shots true and sure!
For target shooting and plinking, any type of powerplant will do, and it is fun to have all 3 to use for either hunting or plinking!