Prop guns are always better but are dangerous in the hands of idiots. Even with modern CGI it's hard to perfectly recreate a realistic muzzle blast. It's also hard for actors to fake flinching/recoiling from each shot while focusing on the rest of their performance (especially if they've never shot a real gun before which is most of Hollywood).
Even with prop guns firing "blanks" you're not supposed to fire it directly at the other person (the camera isn't your eyes, it doesn't see that you're purposefully slightly off aim).