RE: H&R ultra slug?
+1 on the accuracy for the H&R. With the right ammo, the 20 gauge is as accurate as many rifles out to 100 yards or so. My hunting buddy has taken many deer with his- some at 120 yards+ - 1 shot, 1 kill.
If you're primarily sitting in a stand or a blind when hunting, I think it's the way to go. If your style of hunting tends more towards setting up deer drives (i.e. having a lot of moving targets) a pump gun might be a better choice.