Love 16ga: stopping power of a 12ga, but without the kick. I am fortunate that all the local outfitters carry 16ga from Federal. Types available in 2 ¾" shells: 6 and 7 shot size as well as rifled 4/5 oz slugs. A 5-pack of slugs runs $4.95. A 25 round box of 6 or 7 shot size is $9.95. Always in stock here in Nanaimo, on Vancouver Island. Don't know of elsewhere, though. Would love to see shot sizes in 1, 0, or 00 for small to medium game, but the 16ga slug will still take down a large black bear and Roosevelt elk with a single, well placed shot.
When I head out for clay shooting, we usually go all day. After hundreds of rounds, the guys with the 12ga guns are bruised and battered and can barely lift their arms. But with my J. Stevens single shot 16ga, I can still continue and have next to no shoulder bruising at the end of the day. Definite advantages over 12ga.