I love Inertia shotguns. I have Benellis and Beretta 1201FP shotguns, the Beretta is pretty much a Benelli M1 Super 90.
The guns you listed. Franchi, Benelli, Beretta, Stoeger are the only shotguns I know that have a inertia system and rotating bolt.
Franchi shotguns are very nice. They are very nice and lightweight for hunting.
I have only handled a Stoeger at the gun shop, so I can not say how they shoot. But, they seem to be a good shotgun and are less expensive than a Benelli.
Beretta sold a few inertia shotguns, but have stuck with the gas system.
Benelli makes the best in my book. I am not as thrilled with the M2 as the M1.
I don't know about a magazine cut off, but if you need to take a shell out of the chamber simply pull back the bolt and the shell will come out. And the gun will not cycle a round from the magazine unless you hit the release.
As for reliablity and ruggedness, they are very reliable. More so than a gas operated system.
I have shot thousands of shells through my Benelli and not had any major problems. I have had a few jams, but that was during heavty shooting (400 shells in a day) or when the gun is VERY dirty.
Chris