Just bought a Super Vinci before last waterfowl season and absolutely love it. I have had zero malfunctions in all kinds of weather from pouring rain, snow, subfreezing conditions not a single hiccup during a hunt or a sporting clays session. Best piece of advice go and shoulder, swing all the guns your are considering and pick the one you think feels the best yeah the prices maybe steep but a shotgun is an investment and should hopefully last you a very long time. After the success I have had with my SV it will not be replaced in a very long time. As for the 3" or 3.5" debate...I don't shoot them either no need for them but people I hunt with use them and if you ever run out of shells and all other people have is 3.5" you SOL your hunts done. Or if you are in a goose blind and everyone around you thinks the only way to take down a honker is with a 3.5" shell and you don't have anymore 3" again you are SOL. Think of the 3.5" capability as a luxury its like heated seats in a car do I really need heated seats in a car hell no but sure is nice when I slide into my car and it's -20° With whatever you decide good luck. I will take my Super Vinci over any other autoloading shotgun any day of the year, may sound arrogant or fanboyish but I don't care why...because it is what works for me.
If that doesn't light your fire, your woods wet!