If I wanted a "Tactical fighting shotgun" ....I'd pick the semi-auto Benelli M-4 ...its a gas operated gun. And I hear it all the time in gunshops...its a great gun / but its too expensive ...and they don't offer enough "tacky - cool" junk to hang off it ....
http://www.benelliusa.com/shotguns/benelli_m4.php
They list at $ 1,799/and in my area they are selling new for around $ 1625. I think its a solid gun / I've fired a few of them at my local range / nothing not to like about them in my opinion.
I think the argument about pump vs semi-auto reliability is overblown / if you look at some of the better semi-autos on the market today ( not the $ 300 import specials ) .../ but old bias dies hard...
------------------
I just don't subscribe to the idea that everyone needs a "Tactical shotgun" or they are somehow under-gunned ...in the event of something / but then I don't think everyone needs a black rifle either ...
I realize I'm old school / but my primary defense is handled by a Wilson Combat 1911 chambered in .45 acp / and my backup sock drawer gun is a Sig 226 in .40S&W ....and if I have to fight my way to my safe ...there are any number of shotguns and rifles that can come out if necessary ....but an 8 round mag in a 1911 / if you practice with it weekly ( and I do ) is an excellent defensive weapon.
My other issue with many of the Tactical Shotguns / mostly pump guns...isn't really with the gun --- its with the owners - and there are way too many of them that get purchased because they look cool - and everyone thinks they "need one" .../ the owner and his buddies fire 20 rds ..maybe even 60 rds of OO buck with it / or slugs or whatever when its new ....then it gets put away / leans in the corner of a closet or somewhere ...for 5 yrs or more / without every being touched again.
They aren't particularly fun to shoot / they aren't any good at clays / OO Buck and slugs are expensive ( $ 60 for 100 rds or so ) ....and a lot of guys spending $ 250 on a shotgun don't want to spend another $ 60 to fire 100 rds .../ and I get it ....but if its a primary defensive weapon / and you don't train with it - don't use it .../ you're relying on the "image" of it being a perfect defensive weapon ...when you might just be kidding yourself...
Some guys do the same thing with handguns ....buy a gun / put 100 rds thru it ...put it away for 5 yrs ...and think they're protected ...its just as nuts !! Maybe its even worse / because the muscle memory to manipulate a handgun is probably tougher than manipulating a shotgun ....but its still nuts!
In my opinon --- if you think you need a weapon for defense ( and not everyone does ! -- or not everyone should ! --- especially if they aren't going to train with them !! .......but if you do ....buying a pump shotgun, or a good quality semi-auto shotgun ...or a good handgun ....can all be effective ....if you train with them and are competent with them !! Pump vs semi-auto shotgun makes no difference ...
I just wish more guys would think about the time they spend training and shooting vs what to buy .......and then leave it in a closet ! One of my boys is in his mid 30's ....and 90% of his buddies have purchased Rem 870's tactical shotguns ...and not a single one of them has fired their shotgun in well over 3 yrs. My son lives about 4 hours from me ....and we get together 6 or 8 times a yr ...to shoot some skeet, sporting, etc ...and do some handgun training with revolvers and 1911's, etc .... and its not a scientific study ....but in that group of young guys that goes with us to the range ....I just keep asking ...have you shot that 870 in awhile ...and its ...a slumped shoulder, hang head ....no ..... ??? I think its a one in a gazillion chance any of them will every need a defensive weapon ...or at least I hope so ...but if they won't train with them ...I wish they'd lock em up ...until they do.
I think if you ask among your buddies that have them -- its going to be a high percentage of guys that never shoot them ....sadly ...