I believe you are attempting to sneak the comparison past those without experience shooting the weapons in question. I can only guess the ardent military style/high cap mag crowd are letting you or have no first hand knowledge of these weapons.
Lets keep the apples with the apples and discuss oranges later. The AR15 and AK47 use intermediate cartridges pioneered late in WWII by the Germans. The recoil is reduced and thus ability to hold on target for multiple rounds was far superior to battle rifles.
The 5.56x45 and 7.62x39 are not in the same league as the 7.62x51. The 7.62x51 is the battle rifle cartridge modernized. Put into a light AK style rifle and problems abound. Feel recoil is substantial, the weapon has to be beefed-up to withstand the recoil. The civilian version is called the 308 Winchester. For those unfamiliar with the round in question the military version for NATO can send a 147gr Full Metal Jacket out around 2400 fps second using approx DOUBLE the powder charge of the AK which sends a 123gr FMJ out around 2300 fps with HALF the powder of the 308. Using twice the powder on a heavier bullet sure does boost felt recoil. it would take a lot of practice to handle the heavier recoiling weapon and put multiple rounds on target like an AR.
My DPMS, an AR10 clone is a heavy witch compared to the M16A1 I carried. I don't see gang bangers doing drive-bys with my DPMS.
Now the detachable mag shotgun-
Bulky, cumbersome, very muzzle heavy and the mags run in excess of 100 bucks each. Like 100 round mags for your M4orgery, bought by those who lack experience or don't have to carry (or use them) anywhere but the local range.
But I'd imagine the detachable mag shotguns would be limited to at most 7 round mag.
The Street Sweeper style shotguns-
I want to say President Ronald Reagan banned the original Street Sweeper Shotgun back in 1984. They were considered destructive devices. One thing for certain sending 9 to 12 32-33 caliber pellets at your target with each trigger pull takes a lot of the 'aim' out of a close encounter. Except for price/weight/functionality issues would make great mass murder weapons...
I'd opine there is a huge difference between an AR15 in 5.56, and my AR10 in 308. A huge difference between the AK in 7.62x39 and 7.62x51.
And a huge difference between the mag fed shotguns and my tube fed pump.