I think you first need to determine your intended purpose(s) for the gun. The choices will vary depending on your needs. Is it sport hunting, potential survival hunting, defense against critters 4-legged, or 2-legged. Handguns are useful & compact, but I assume they are not an option in your jurisdiction.

The AR-7 & M-6 are both a little anemic for defensive purposes. They're not unusable for defense, but they don't seem attractive as a deliberate choice either. If the individual gun functioned reliably & shot accurately, it could be an adequate harvester for small game. The M-6 adds a lower powered shotgun (.410) which could be helpful for guaranteed ground sluicing of a nearby bird or other small edible. The AR-7 adds quick repeat shots, a useful feature if multiple opportunities present themselves simultaneously. The M-6 is available in stainless steel, something that should be desireable for a boat gun. Somehow I can't get excited about either as a hunting gun. Maybe its the esthetics.

If defense is important, a larger caliber/gauge is desireable. Ammunition in 20 gauge is somewhat lighter than 12 gauge. You can also get pump shotguns and some lever actions in stainless steel. Unfortunately they they will still be heavy & bulky. Marlin has a lever action in stainless steel in caliber 30-30. A blued steel lever action might be available in a takedown version. A .44 Magnum fired from a rifle is a competent hunting and defensive gun. The ammo is lighter than 12 gauge & can be loaded up or down for big or small game.

Incidentally, the older Savage 24 combination gun was made in the middle 1980s in various rifle caliber, in 20 gauge, and in nickle plating. Unfortunately, I was not pleased by the quality of the nickle plating I saw. The Camper model, 24-C, weighed about 6# in .22LR/20gauge. The stocks were wood. They are a little hard to find, but they are occasionally available used. I don't think they've been made since the later 1980s. I personally like these older Savage 24s. My kids & I love to shoot ours.

Good luck,

John