I think many people get "locked into a concept" because they have heard a pump is the ONLY way to go, Pumps are more reliable, the sound of a pump will cause a BG to fill his pants and on and on. I have pumps, semi autos and over and unders.
There will always be differences of opinion, just look at the Remington 870 VS Mossberg threads. As far as I am concerned, neither holds a candle to an Ithaca 37 and I own Rems and Ithacas. Personally, I never cared for the looks of a Mossberg.
I also think a lot of it has to do with PRICE. Some just may not be able to afford a semi auto. For some reason, they will fight tooth and nail that their shotgun, although cheaper than your, is FAR superior.
I have heard all the stories why pumps are better and again it is just an opinion.
I put out a challenge some time ago that I would put a 100 dollar bill on the fact I can shoot 5 rounds through my Berreta 390 faster than you can through your pump of any brand. I wasn't even throwing my Benneli into the mix to keep it fair,,, sorta. Actually, I'd put the Benneli against any pump or any one. Simple fact there is NO way you can shuck a shell out, pump one in and pull the trigger FASTER than I can simply pull the trigger. I think Tom Knapp has proven this time and again.
I have noted in the past, for HD I will stick with my semi auto. I can operate it one handed if needed and that is always a possibility. Can you operate a pump one handed?
I have never really seen the need to put one or the other down. If you have a pump, so be it, if it is a semi, so be it. But for people to come out and say a semi has no place in HD is simply not intelligent.
Finally, as far as gas seals go.. I think the 1100/11-87 are the only ones with a neoprene washer that acts to seal the gas. I used a 1100 for 1,000's and 1,000's of shots at Skeet and never had a problem. I actually made a trip to the hardware store and bought some replacement washers and change them occasionally, when I think of it every couple of years.
As a side note, I had a lady friend that had an 1100 she used for skeet, it finally quit on her. Reason: she never cleaned it and it finally loaded up with carbon and crap. We were at a match and between strings so I wiped it down with WD-40, back in action, even though the gas seal was missing, the 1100 still functioned.