This question comes up in EVERY forum I belong too. There will NEVER be an agreement on which is best, be it a semi or a pump or a double, buckshot, birdshot, slugs, the sound of a pump racking a round, a bolt slam home or a silent loading.
I have a few "personal" choices and "personal" thoughts.
First off is too many watch too many Rambo type movies and have no idea of real world shootings and HD situations. People just immaging themselves as Rambo. Nice concept, just not real world HD.
I have a Berreta 390, old model, wood stock and it never failed to fire, not ever. I also have a Remington 870 and an Ithaca 37 available but for MY home defence, I want a semi, my Berreta.
What happens if for some reason the nasty invader gets off a shot and disables your arm, how are you gonna "rack another round"? With a semi, I am sure I can continue to fire one handed, difficult but doable.
As mentioned a couple of times, why would I assume the sound of me "pumping" my 870 is going to make the BG run away? He may,,, then again he now knows where you are. I don't want him to have ANY idea of where I am. I most likely will be behind a door frame somewhat protected, close to the floor where he won't expect me to be anyways. I now have a bit of surprise in MY favor because I am NOT where he would expect me to be.
I don't have extended magazines, side saddles, bayonets and all the other crap that is so popular with the unknowing. If I can't defuse the situation with one or two shots, I am doing something wrong. I sure don't expect a running battle requireing me to have 30 rounds attached to the gun (see Rambo mentality quote)
As I said in the beginning, this will NEVER get resolved as there are simply too many OPINIONS out there, most unfounded and based on watching too many movies.
Whatever...