This is an opinion question. Each has their own following and each is equally satisfying to the individual user. So there is no "Better" category, Just followers of the individual sports.
Nearly everything. Paintball guns are fired through the use of air or CO2. Also they shoot only paint. bb Guns shoot pellets, and look completely different then most paintball guns.
Neither. Both perform as intended. Pellet is more accurate and more expensive. ADDING: If you like to shoot rapid-fire, there are more options for semi-automatic guns among BB guns. A round steel BB is easy to load and to make a gun self-loading (loads into the chamber). Most pellet guns have to be loaded by hand, one shot at a time, although there are a few models that use 5 shot clips that look clumsy to use.
They run on the same concepts, having a compressed gas propel them. But bb guns are generally more powerfull, slower shooting, "classic" looking rifles and pistols. Paintball guns are either military simulation or built specifically for the needs of paintball players, that look nothing like real guns or bb guns.
They would be better than 14 BB gun.
They are not. It is against the law to own them as well as BB guns. Nerf are fine
It is legal to own air rifles in Pennsylvania, but it is not legal to hunt with them, even with a license.
No. Airsoft is a type of sport like paintball so airsoft guns you can shoot people. but please shoot responsibly.