As far as quality goes, I don't think there's anything to worry about from either make. They're the best sellers for a reason.
But you do get either Beretta or Browning people. It's mostly down to which type fits you best. In general terms, as has been said, a Browning tends to be a bit heavier and for that reason is better on the clays. The Beretta is better on the pheasants because it's a bit lighter. Easier to whip into action at short notice and not as tiring to carry around all day. But we're talking little differences here really.
You also have to decide what looks best for you. I know that's perhaps seen by some as not as important, but as it's a buy to last for a good proportion, if not all of your shooting life, you're going to have to be happy looking at it a lot. Hence the differing grades of guns, often with exactly the same internals.
As has been said, before deciding, the least you need to do is handle each model on your shortlist and see how it mounts and swings and indeed if it fits you. Ideally you need to be able to narrow it down to perhaps a couple of guns and then see if you can have a go with them. Either see if there's any at your nearest clay ground to hire, perhaps blag a go with a friend who has one or if you're lucky, the gun shop you frequent may have somewhere to try them out.