A riddle about Russian Roulette

[Zundfolge]

Ok, so here's the scenario.

You're forced to play one round of Russian Roulette with some "badguy". The rules are simple. You will be allowed to choose a double action .357mag revolver from the following selections:

1) S&W model 686
2) Colt Python
3) Ruger SP101
4) Taurus model 66

You will be required to select the loaded and pre-spun revolvers from the list, it will be put in your right hand and you will then promptly put it to your head and pull the trigger double action. The one twist is that you have the option of pointing the gun at your opponent and pull the trigger but if you hit an empty chamber your opponent can pick up a fully loaded gun laying on the table and shoot you in the head with it (so you'd only do this if you knew for SURE you were going to hit a live round).

So which gun do you pick and why?