If you're shooting over decoys from a blind, stay with a full choke. If you're jump shooting birds from creeks or dugouts (stock ponds), I'd go with modified. To be sure, check the pattern at thirty yards for both chokes. Shoot a big sheet of paper (scotch tape a couple pieces of gift wrap together). Some full chokes don't do well with steel. Number 2 shot is not a bad choice. Back in the days of lead I preferred #4 but the rule is jump up a size for steel. Also, make sure you are shooting the fastest loads you can buy. Forget about magnum loads in steel. They're too slow and will not penetrate sufficiently. Slow magnum loads were okay for lead but a waste of money in steel. You don't need more shot in the load but rather more care in selecting and taking your shots.

Most of my shooting is flooded timber shooting Wood Ducks and the occasional Mallard. If I were hunting decoys or open water I would use a tighter choke.

Full

I shoot a Model 12 Win with a poly choke. I shoot sub modified on the choke over decoys. I shoot # 3 steel drylocks 1 1/4 oz. Very few ducks or geese don't die at my blind. I killed 3 geese with one shot Tuesday. Glock enjoyed the retrieve.

I like to use a mod or a full. Depends on where I am set up at. In the river I like to use a full. Its a smaller river and a close shot. In the swamp I go for mod gives a bit more of a distance shot.