If you are going to shoot steel, you will want the 3.5" for long range ducks, and especially for geese. If you will shoot tungsten, hevi-shot, etc., the 3.5" is not really needed. My understanding of turkey loads is that the best patterning load is likely to be a 2.75" one, so you may not need a supermag for that, either. Having said that, the 3.5" guns are very versatile, so you may wish to spring for the extra $ so you won't wish later that you had. Some (all?) of the 3.5" autos will not reliably function with light target loads (less than 1-1/8 oz). Personally, I shoot the big 12 for waterfowl (and turkey and deer if I hunt them with a shotgun), and a 20 ga. for everything else.