I jumped on the 3.5" train when I first got interested in hunting waterfowl and turkeys. I bought a Mossberg 835 and was rolling out 3.5" turkey and waterfowl loads and buckshot. Started getting bad habits, so I decided to see what the difference the 3" would be. Ever since I have stuck to 3". 3.5" gives more numbers, but 3" will kill just as dead and I have seen when the pattern is more even in a 3". I still hunt with the 835 and like that I have a choice in all sizes, but I hunt with 2.75" for dove, rabbit, and so forth and 3" for turkeys. By the way, imo, duck hunting isn't what it is cracked up to be, too cold and too dag early. But I love when a buddy brings me one to eat. Good Luck!