If you like a 20 you'll love a 28. Ammo is a bit pricey. I carried a Silver II 28 grouse hunting for many days at a time in the U.P., perfect grouse and woodcock gun.
Since I already own a 12 Red Label Woodside this would be my choice for a new O/U....
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=378187023 h.h.