My first turkey gun was the NEF 12 gauge single shot in the original MO Bottomland camo. It did not have the heavier 10 gauge type barrel on it, but it was chambered for 3.5" shells. I shot that thing exactly 4 times before I traded it on a Mossy 500 chambered for 3". Shooting that thing 4 times made my right shoulder, my right arm half way to my elbow and my chest all the way to the sternum black and blue for days.
It was a joy to carry, but pure punishment to shoot. I can remember tangling with a really big dominant bird one spring day, took him 90 minutes to work his way in. At 11:59am, I caught movement and cocked the hammer on the NEF, fearing that recoil...that big bird stayed hidden until 12:01pm, and then stepped out into the clear, shooting hours over. I was somewhat relieved, great hunt, no bird but no loose teeth in my head either.
I carry a Winchester 1300 with synthetic stock and a 21" barrel. Almost as light as that NEF single shot, but shooting the 3" shell. Never had a bird get up and get away.
Changed over to the Hevi 3-2-7, I think this is about a potent turkey-getting medicine as you can get your hands on.
To each their own, but I don't see any need for a 3.5" shell when there are so many awesome loads available in the 3" hull.