The Beretta 390 seems to be the gun of choice amongst clays shooters. The Beretta comes with shim kits that make fitting easier and there are a host of aftermarket parts to make it function more reliably.
Right now the 390 can be found at bargain prices because Beretta introduced the 391.
The 1100 is a great gun and Remington has brought back the Trap and Sporting Clays model. The Wall mart models are not as nicely finished as the clays models.
For Beretta parts try Cole Gunsmithing www.colegun.com
they are the gurus when it comes to the Beretta. they have replacement parts that will extend the life of the gun and lots of other goodies for the 390.