I am not sure when or how it happened, but the almost ancient Browning recoil principle is now "inertia". Show business.
A gas operated gun bleeds off some gunpowder gases to start moving the action parts of the gun to accomplish a reload, and in the process spreads the recoil forces over a longer period of time, thus reducing felt recoil. In many cases significantly reducing same. But, the gases contain unburned carbon, etc., and over time they will get the gas system of the gun dirty enough that it will quit working. It is generally quite easy to clean the gas system, but some people seem to think it is a deplorable problem, ranking ahead of having to take out the garbage. Some gas systems resist getting dirty better than others. I have limited experience with a variety of gas systems, but I would think any system that would run 300 heavy Blue Dot reloads would be incredible.
In a recoil or "inertia" gun, the recoil gets everything moving, and you stop most of the gun while the right action parts keep moving to accomplish a reload. In the old Browning long recoil process the barrel and bolt proceeded all the way to the rear locked together, then just the barrel came forward and then the bolt with a shell. Some folks could feel all the different actions and called it the Browning shuffle. I found it unnerving. Recoil and/or "inertia" guns do not mitigate felt recoil to nearly the same extent as gas operated guns. I was considering a Benelli 3-1/2" Super Black Eagle back before the better non-toxic shot came along. Man, it felt good! But, after several shots seriously threatened my dental work, I turned to a 10 gauge. The "inertia" guns do not get dirty from unburnt powder gases because they all go out the end of the barrel... well, 99.999% anyway. The rest wisps out the ejection port. Therefore they will usually go a lot longer than a gas gun between required cleanings. Because of the greater simplicity of the system, they can generally also be built lighter while being every bit as strong. If you do not particularly like recoil, this may not be a good thing, if
you shoot heavy loads. The old Franchi 20 gauge 48AL is I believe the lightest thing I ever saw, and with quail loads it was great, so many years ago a friend got a 3" magnum 12 version, and with full out goose loads it was way worse than my 870, which wasn't heavy itself.
Both systems have their proponents, and like most things in 'Gundom', no amount of facts and/or data is going to sway anyone's opinions, much less change their mind. Lately the Benellis seem to be the trendy choice over here as well. Anyone having a raffle likes to use them. I'm quite content with my first generation Model 1100s. I don't mind keeping them clean and they work for me, and I have no plans to go to Argentina to shoot 500 times a day at doves. But if I did I think I would prefer to take along a little spray can of RemOil and an old sock than to change my ways.