Thanks to everybody for the wealth of information in your responses. I am learning a lot from the responses. The main thing I have learned is that the most important thing with any gun is USER TRAINING and being practiced and experienced with the gun he chooses and to have a gun that fits him and he is comfortable shooting. If I choose the Pump it will probably be the 870, if I like the fit and feel. If I go with the Auto....Hmmmm....I don't really want to have to deal with gas operation and would want the simplicest mechanism. I have the S&W 916-A, which I want to replace, in the closet which I have never shot and I have a full box of NO. 8 shells too. It would be wise for me to shoot up that box of shells plus more and get the "feel" of the pump before I buy another one. The only shotguns I ever shot were single/double barrels and bolt actions. When I was younger I did a lot of shooting so I do practice proper gun safety.
When I make up my mind and make a purchase after checking out different guns for feel and fit for me, there is a place I think I can possible go to and shoot a lot even if I have to become a member and that is the gun and skeet club where I live. Great, Huh? I am 55 years old now. When I was 14 I went there as a jr. deputy with the sheriff's deputies and did get to shoot 4 clays and I hit em all. It was fun. We shot 22 rifles every Saturday for about 10 weeks, got to shoot pistols and got to see a Thompson Sub Machine gun fired. We even got to tour Louisiana's Angola State Prison, New Orleans Parish Prison and they took us to an LSU football game. Everyone needs to tour a prison. Makes you think twice about committing crime. Sure got my attention. I seen enough to know I never want to go there.
Ammo Choice. You guys gave many good opinions on which ammo to use in different enviornments. I live alone so for me it's probably gonna be 00 buck or No. 4 buck and can't forget about slugs depending on how they shoot in the gun I purchase. My nearest neighbor to the North is over 150 yards. East about 100 yards is a gravel pit office inhabited during the day but not at night. I have no wife, no kids which means no help, no backup. My only "friends" here in a hostile situation are Mr. Sig Sauer, Mr. Smith, Mr. Wesson and Mr. Peter Beretta and the "punch" they carry directed by me. They need to carry a powerful punch. I like what I read about 00 buckshot going through walls and here is why. If a BG "thinks" he is safe behind a wall in MY house after he has damaged my property by forcing his way in trying to get me or what is mine, I want him to rethink it as he lays on the floor after them OO's reached through that wall and got him. When my only gun was my S&W Mod. 66 357 I loaded it then and still today with staggered hollow point and FMJ. The first shot is HP looking for flesh. The second is FMJ in the event I miss with the HP and he or she ducks behind a wall. So, I live alone and the "friends' I have with me must pack a powerful punch, even enough to disable a vehicle......getaway vehicle.
I have a monitored alarm system. My wakeup to alarm weapon of choice, which is a one second grab on the night stand, is the P226 9mm. The shotgun would be my choice for a stranger knocking at the door who after knocking for a while decides to check the door knobs to see if they are unlocked. That's where the "click-clack" sound of the pump may come in handy or even better.....Ker-Chunk. I just learned those two words from other good reply posts. "Click-clack" sounds scary but KER-CHUNK sounds DEADLY. Another term I just learned is....shortstroking. Hmmm, that could be a problem but after training with the gun enough it shouldn't be a problem or at least I would know how to deal with it. I know any gun can fail. Having a backup would be the thing to do. Backup to the shotgun, for me, would be the P266 or mod. 66.
Finally, if you're wondering why all the concern or paranoia, here is a true story that happened to me. I lived alone in a mobile home next to my mother's house. One Christmas Day, in the early nineties, after going back to my trailer after the family get together I heard a car drive up while I was watching TV. A passenger gets out, comes upon the porch and starts knocking. I look through the peephole in the door and recognize the guy as one of the customers that used to come to my parents grocery store. He had and still has a record for theft and dope a few miles long. Well, he continued to knock but I played possum and was very quiet. Then, I heard him check the door knob to see if I had possibly left it open. Then he walked to the back door and checked that door. THEN....I GOT MY P226. My heart pounding, I said to myself....Oh S....T. Then, he climbed on the tongue of the trailer and proceeded to try to take off the screen to the window. Heart really pounding now. I stood in the hall shielding myself, gun aimed at the window. He was trying to pry out the screen and the window. Thoughts flying through my mind........."Am I gonna have to shoot this Bastard? Legal implications. Living with the thought I killed someone. Is this amount of force necessary in this situation? Teaching career. jail?......ANGOLA?????" The intruder at this point decided to give up and leave. Whew! I called the Sheriff's office. They came over and saw where he tried to come in. They arrested him. He admited guilt and served about 10 to 12 months for his actions. Was he armed? I doubt it. Would I have shot him if he had broken in the window and actually jumped in the trailer? I would have. However, I'm glad things turned out the way they did. Woulda been nice to have a KER-CHUNKER.
. Others have answered your question well. Auto vs. Pump just depends on how much you want to spend and which you want to spend some time with. It's the software after all as long as you have quality hardware. I've owned a few autos, Rem 1100 being one of them. If I were buying another it would be either the 1100 or 11-87. I also had a crappy Chuck Daly that liked to light strike primers. Not good. 
