I figured that you would get some good replies to this question, and you have. My .02:
A gun is a tool. Every tool has specific uses for which it is best. Get the tool that is best for the uses that you foresee.
Are you going to just leave the gun at home or in your desk during the day, or will you carry it concealed? This makes a big difference. A revolver will be harder to conceal due to the width of the cylinder. If concealment isn't an issue, then a revolver may be just as good a choice as a semi auto.
Barrel length: If you choose to carry a revolver, you may think that a snub nose (say 2" barrel) will be easier to conceal because of the shorter barrel. Not necessarily. It's usually the width of the gun, not the length of the barrel that makes a gun visible under your clothes. A revolver with a 4" barrel will conceal just as well as a snub nose, plus it will shoot easier.
Caliber: There are a number of calibers which will effectively stop an attacker. I prefer a .45 auto because the round is big, wide, relatively slow moving. That equates to less penetration (less chance of it going completely through the attacker), plus it hits like a sledge hammer. Something like a .357 (which is a fine defense caliber) may cause more internal damage, but not necessarily stop the attacker as quickly. Remember, the first thing you have to do is STOP the attack. It does no good to put a fatal round or two into an attacker who is high on some wierd drug, or just crazed with adrenaline, only to see him continue to attack and kill you. When the round hits, you want the bad guy to fall. Others may disagree with this theory, as it is constantly debated, and I know that I don't get the last word on this point. I respect all mature and respectful opinions.
No matter what you choose, get some training as you have already talked about. The NRA can give you a list of certified instructors in your area.
Practice, practice, practice. If you ever have to use your gun in self defense, God forbid, it MUST be a natural action for you to draw and fire effectively. In a life or death situation, you probably won't have time to think a lot about the things which should come naturally because of your training and practice. If you do have a lot of time to think, then it probably isn't a situation which needs to be resolved with a gun, and you can probably get away.
Congratulations on your decision to take responsibility for your own safety and that of your family. Our LEO's, God bless them, can't always be there watching at the crucial moment. Choose not to be a victim.
2003 MM 300A
Born June 18, 2002
Adopted Christmas Eve, 2002
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God and the soldier we adore, In times of danger, not before.
The danger gone, the trouble righted, God's forgotten, the soldier slighted.
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Cynicism is the smoke rising from the ashes of burned out dreams.