Depends on what you are comfortable shooting. A5 is a short stroke inertia system whereas the Beretta 300 and 400 series are gas operated systems. I own both. The A5 is finicky if you do not set it up correctly. The Beretta is also softer shooting so if you are strictly comparing these two semi shotguns, the Beretta is the clear winner.
I personally prefer to shoot a long recoil system such as my Binelli M3 which cost over twice as much as the A5 and the Beretta and is restricted. For hunting I use a 1960s Belgium made Browning Auto5 light 12 which is what the M3 recoil system is based on. I just prefer the mechanical feel of the recoil system. A nice Auto five could be bought for a third of the price of the new A5 or 400... about $4-500.
Alternatively, I have been very impressed with the Mossberg 930. Since I picked one up about a year ago, it hasn't let me down yet. I picked it up because of the positive reviews and the fact that it was $530... for a brand new gas operated semi!!! I would say that the 930 is the best value for the money in terms of new semi auto shotguns. The Beretta fits me better and it doesn't feel as bulky and boxy as the Mossberg but the 930 isn't so bad that I would say 'no' to it completely. The feel of a shotgun is very subjective and personal and that being said, my 930 reliability, recoil and performance is pretty close to my Beretta, IMO.