Pump preference.
In choosing your next shotgun, keep a few things in mind.
Even though the technology involved with semi-auto shotguns has changed/improved dramatically in recent years, they do still require a little more maintenance than your average pump. If it will sit behind your door or a truck seat for a while (like mine does) you may consider sticking with a pump.
Another consideration is modification. Do you want an additional barrel? How about an extended magazine tube? Sidesaddle or other accessories? Due to the large amount of use pump guns get from LE and the HD market, these accessories are generally somewhat cheaper for pump guns. Also, they are slightly easier to install on pump guns.
A third consideration is size/weight. It has been my experience that my pump guns have generally been lighter than my autos.(I have had a couple of each). Also, the pump guns seem to be bit less bulky than the autos.
All that being said, my current and only shottie is a Mossberg 500. I have a 20" barrel and tube extension that rides on it for SD. I also keep a 24" barrel in the closet as it makes and excellent feild gun.
If you are dead set on a semi-auto, may I suggest the Benelli Nova and Super Black Eagle series. Both are designed to be feild guns, but I am sure that any good gunsmith can make any changes you like, including barrel length. They are also both a tad less expensive than Beretta's offerings, and just as much gun.
Good luck to you, whichever you choose.