The guys over at shotgunreport.com say the Berretas are the Best Buy on the market. Longevity is nigh legend, and the adjustable stock means it's easier to get fitted than most.
I own the earlier 390 and think it's a good gun and the 391 is supposed to be even better. There are a lot of fans of the Beretta gas guns particularly because they can handle light loads right up to the 3" magnums.
I own a Gold Sporting 391 12/28 and I love it. I shot it all last season on pheasant and pigeon. Great to carry and great balance. I've put about 1000 rounds (skeet and field)through it without a single problem. I shot several boxes of low-recoil 1 oz and never had a problem. A great gun.
I've got a BPS with the synthetic stock and I love it. It's great in the duck/goose blind or out in the field. They're indestructible.