Here's the Montefeltro:
http://www.benelliusa.com/firearms/images/montefeltro-gr2-12ga-large.jpg
And here's the Super 90:
http://www.benelliusa.com/firearms/images/m1-wood-large.jpg
I believe the Montefeltro and Super 90 share the same buttstock, receiver, and internal parts. The Montefeltro has a stylized cut into the side of the receiver, but I believe the receivers are otherwise identical.
But take a look at the forends. The Montefeltro's forend is considerably longer.
Here you can see the various stock options that Benelli offers:
http://www.benelliusa.com/firearms/accessories-stocks.tpl
Note that the Super 90 and Super Black Eagle have interchangeable stocks, while the Montefeltro's longer forend prevents full interchangeability with the Super 90 and Super Black Eagle.
Here are the extended magazines that Benelli offers:
http://www.benelliusa.com/firearms/accessories.tpl
The Super 90 and Super Black Eagle accept the same magazines, because the magazine on both weapons is hollow all the way to the front, and both magazines can be extended very easily.
Here are some of the barrels that Benelli offers:
http://www.benelliusa.com/firearms/accessories-barrels.tpl
Here we see non-interchangeability between the SBE and Super 90, because the SBE's barrel extension is longer and basically forms into an upper receiver. However, the magazine lug on the bottom of both the SBE and Super 90 barrels is identical. The magazine lug actually encircles the magazine tube on both weapons, permitting the fitment of extended magazines.
I contrast, note the magazine lug on the Montefeltro's barrel. It's small and doesn't encircle the magazine tube. It only encircles the threaded stud on the tip of the Montefeltro's magazine. The Montefeltro's magazine cannot be readily extended.
To me, the non-interchangeability of parts between the Montefeltro and the Super 90 puts the Montefeltro at a disadvantage. For example, I have three Super 90's. The first is the Field version with walnut stocks and a 24" barrel. The other two are Tactical models with 18" barrels and ghost-ring sights. One Tactical has a standard buttstock and the other has a pistol-grip buttstock. All three shotguns have the seven-shot magazine fitted and are loaded with Federal attenuated Buckshot loads in the magazine and on the shell lifter (empty chambers), and then hidden in different parts of the house. All of the parts among these three shotguns are interchangeable. I have a spares parts kit and that spare parts kit works on all three guns. All three guns operate in exactly the same manner and handle similarly. When I go to the clay target range and fire 500 rounds, I get a lot of practice with my Tactical models as well, because they are so similar to my Field. I always shoot "low gun" no matter what the rules permit, and get to practice 500 or more speed mounts every time I go and play at the clay target range. This practice really kicks over to the Tacticals, more than you might think. I like this set-up a lot, enough to like the Super 90 over the SBE for my own needs.
To me, the Super 90 is just an awesome shotgun. It could be improved though. I wish the barrel extension had the same design as that of the SBE so that sights could be interchanged with barrels. The older Benelli 121 also had this design. For some reason, Benelli went from that design to the Super 90's design, and then back to the older design with the SBE. The Super 90 also has that cheap shit BB gun safety. A tang safety similar to the ones fitted on the Mossbergs and the Browning BPS would be far superior. Other than that, the Super 90 is just awesome.
