I don't think you can go wrong with either gun. A 3" chamber is enough / especially since you won't be hunting anyway. The only time a 3 1/2" chamber may become an issue is on Geese primarily / and even then a gun chambered in 3" is fine for me personally.
In general, for clay targets on a pump gun, I would go with a 28" barrel. It gives you a longer sighting plane - and will smooth out your swing a little.
I like the Benelli Comfort Tech system / I have it in a semi-auto model - the Super Sport - but that's a different animal.
In terms of prices / 2 places - and quit shopping ..... DJ's in Bothell will be cheaper than most / or Kesselrings in Burlington. If DJ's Loan and Sport in Bothell doesn't have one in stock / he can order it / get it in a few days. I'd be shocked if Kesselring doesn't have it in stock.
A gun you haven't looked at is the Browning BPS / its my favorite pump gun. They make a synthetic / but the walnut stocked Hunter model is a nice entry level gun as well.
http://www.browning.com/products/cat...12&type_id=211