Actually..and not to get into a pissing contest here..the BM4 is offered in quite a few different variety models. Albeit the heart/primary nomenclature of receiver-barrel-system does not change, but that is also fairly standard of how other shotgun manufacturers offer their platforms.
The BM2 is a terrific overall & lighter platform vs. the M4. The M2 has been proven extremely successful/popular, particularly amongst 3-gunners and other competitive shooters..where it is often tricked out/customized & further lightened in weight than factory OEM.
However, sticking to & emphasizing reliability in any/all environmental conditions?..the ARGO system of the BM4 always comes out on top vs. the inertia system of the M2.
This is because the BM4’s ARGO system utilizes a short-stroke, 2 stainless steel piston design that totals only 4 parts. It has been compared numerous times vs. the M2 and validated the BM4 design cycles faster..and also against the Beretta 1301 which utilizes a long-stroke design piston system that involves more parts and results in slower cycling vs the M4 system.
Totally concur regarding technology advancements and users embracing change vs. never changing. I am a long time owner of a variety of 1911’s, I always stuck my nose in the air & dismissed any mention of the newer 2011’s. Then about two years ago I handled & thoroughly shot an Atlas Athena double stack, incomparable trigger, highest quality & performing semi auto pistol shooter I’ve ever experienced..so I custom configured & ordered and now my Athena is my every day CCW cocked & locked complete with RDS(also used to be frowned upon!)
Also agree regarding Youtube videos, etc. Flannel Daddy makes a video advocating how great a product is and then the price doubles..or he shits on a particular LPVO and that makes gospel with internet trollers without real user experience.