I have heard many firearms instructors say he who has the most bullets generally wins the gun fight. These are those that are defending the pistol side of the argument (also referred to as semi autos). What is meant by semiautomatic is every time you pull the trigger it goes bang. You do not need to pull back the hammer every time to ready the gun for firing, the recoil of the gun being fired cocks the weapon for firing another round. Semiautomatic pistols are able hold more bullets. They have a wide range of capacity and this depends on caliber and frame size of the gun. The most common average holding between 12-17 bullets.
Revolvers on the other hand usually hold 5-6 bullets. This might seems drastically inferior to the high capacity semi auto, however the revolver, like the card slick that carries one in the movies, has an ace up his sleeve. That ace is known as reliability. Now most semi automatic pistols are not known for malfunctioning on a regular basis, unless you are my brother who shoots limp wristed. The revolver is simple and easy to use. If the zombies were invading your house you could literally hand the gun to grandma and say aim for the head and she would be able to do just that. Revolvers are simple and easy to use and they go bang as long as you keep fresh bullets in them. Let's just hope that less than seven zombies are invading at one time.
The question is do you want to risk having the slight chance of a semiautomatic malfunction in order to have the option of carrying more bullets or would you prefer to employ the K.I.S.S. (keep it simple stupid) model with a revolver? In other words who do you identify with more Jack Bauer or Dirty Harry?
You could always just buy both if you are on the fence.