The Maxus has only been on dealer shelves for only a few weeks, so it would be difficult to get much feedback on it.
My impression is that Browning developed the Maxus in order to better compete against the Extrema 2, as it was clearly superior to the older Browning Gold autoloaders.
My experience with my Extrema 2 and Browning Gold shotguns has been that the Brownings do tend to have slightly lighter recoil. If this new Maxus does have an even better gas system as Browning claims, then I imagine that it would win out over the Extrema recoil wise.
The Extrema 2 has a trigger that is far superior to the Browning Gold shotguns. But Browning claims that the new Maxus has a brand new trigger system that is top notch. How did the trigger pulls compare to you when you handled both shotguns? Did you have a preference?
I would say that you should buy the gun that feels most comfortable for you to swing.
I personally like a heavier gun. I think it makes your swing smoother, and provides more momentum so that you don't stop your swing, which is easily the biggest mistake that shotgunners tend to make when shooting.
But I've never held a Maxus, so I definitely cannot comment on how it feels. But it is 3/4 of a lb lighter than the Beretta Extrema 2. So I have got to believe that the guns are going to have a different feel to them when brought to the shoulder.
If you don't care about hunting geese, and plan to just shoot 3" Magnum loads when duck hunting, another option would be the Beretta 391 Urika II. It is almost as light as the Browning Maxus, being only 1/5 of a pound heavier.
The bottom line is that you should buy the shotgun that feels most comfortable for you to swing.