Criminal with a gun.
Cop with a gun that thinks you are a criminal.
because you can defend and prove your innocent (Unless you are a criminal) with a cop.
Just because a cop thinks you're a criminal doesn't mean he's gonna kill you. A criminal doesn't care about the well being of others and would be more likely to kill someone he doesn't care about to get his way. A cop isn't trained to "shoot first, ask questions later," so if you don't act like a moron, you won't get shot.
A criminal could kill me. A cop could arrest me, but if I'm innocent I would be fine after he finds out.
The cop can call backup.
As we have seen over the years, cops can be violent and, in the heat of the moment, can definitely mistake you for someone with malicious intentions. A criminal could kill you, but he would probably take your money, and if you resisted, he might shoot you.