If you keep your shots under 40 yards IC would be my choice. Steel #3 shot on big ducks, #4 on wood ducks and smaller and BBB on Canada geese are what I use. I would suggest that if you go for geese and the shots are longer go to Light Modified. Remember that these chokes usually will pattern steel shot tighter than lead shot. For example, my Briley IC gives me a modified pattern at 40 yards with steel shot. When we get lots of birds decoying well I often put in a skeet choke.
One advantage of extended, aftermarket chokes is you can see what choke is in the gun with a glance. There is a huge amount of marketing hype applied to chokes and shells for waterfowl. Contact Briley manufacturing in Houston. They are first class and stand behind their products.
If this is going to be your first season with a new gun get out and shoot it every chance you have before the start of the season. Shooting several hundred clay targets with lead shot will save you money in the long fun as you will be a far better shot.