It really all depends where you get hit
Yes they do, they fire metal balls at much higher speeds.
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.
Both can be dangerous if used improperly
Pain is different for each person. But in general, CO2 Powered would be more painful. Because of the constant speed of it in general.