Mossberg 935 w/3 1/2" chamber will shoot just as far and kill just as dead and since you are already a Mossberg fan the learning curve will be shorter. They might be throwing more pellets out there but they won't go any faster or farther than your load and more pellets won't make up for poor shooting. Get some boxes of 3" shells and enjoy the day.
Unless you really crave a new gun I would stick with what you have, the 535, smile nicely and gather up your share of the ducks. I like my 10 gauge a lot but for serious social work it isn't the gun I grab. If you get the Ithaca let us know how it works out for you but I'm thinking your body would prefer the 12 gauge.
Good intentions will always be pleaded for any assumption of power. The Constitution was made to guard the people against the dangers of good intentions. There are men in all ages who mean to govern will, but they mean to govern. They promise to be good masters, but they mean to be masters.