Free: Contests & Raffles.
I don't shoot 3-1/2" to much, as I can work them in close and kill them fine with 3". If your looking for a 3-1/2" gun, you gas auto loaders will have the lightest felt recoil. Your inertia guns will kick a bit more. I prefer inertia though, as they are super simple to clean and maintain. They swing fast. I shoot the Benelli M2, 3" only & SBEII which shoots 2-3/4" to 3-1/2". My boys shoot the Winchester SX3 & SX4 shotgun. Cost was the factor for my boys as the Winchesters are about half the price of the Benelli.
I remember when Mossberg came out with the 12ga 3.5" in a pump in the 90's. We bought one and I took it to an "end of the year" high school class party. We were shooting clays and I handed a kid the shotgun. The first round was a low base 8 shot and the second was a 3.5" T shot.The kid missed the first shot, pumped it and then let go the 3.5. It was one of the funniest things I have seen, he thought the shotgun blew up on him, he grabbed his shoulder and thought he busted his collar bone. He was done shooting for awhile.