alls 3 1/2 12 gauges do is bust your face up, they may have more shot than a 3 inch, but travel at less speed, carrying less kinetic energy, and typically pattern like crap, as far as shells go. but there is one good thing about a gun capable of shooting 3 1/2 inch shells, unless its a mossberg, because there is nothing good about those. The advantage is this, shooting a 3 inch load in a 3 1/2 inch 12 gauge gives you better patterns, due to them having a bigger bore. My 870 express supermag is about the deadliest turkey gun I have ever shot, I put on average of 35-40 pellets in the head and neck at 45 yards shooting winchester XX turkey loads ( 2oz #4's). I dropped a bird at 49 yards this past spring. As far as goose loads go, if T's pattern good in your gun use em and nothing else. BBB is ok if thats all you have or can get to pattern well in your gun. anything smaller than T's or BBB's are duck loads. As sportsman you should always use the largest shot that works well out of your gun that you can handle, this is to make cleaner, quicker kills. Like when I hunt whitetail I use a 300 win mag with 180gr failsafes, yes its way overkill, but I have never lost a deer that I have shot.