Although I understand your point, there are a few tradeoffs... shotguns are generally large and the ammunition for them is even larger. This limits the amount of ammo you can carry. Also, rifled slugs out of a shotgun aren't exactly the most accurate projectile out there... I've always preferred accuracy to "knock-down" power.
Part of my prejudice comes from encountering too many "good ol' boys" with shotguns following a "blood trail" because they didn't take the deer cleanly in the first place. That's no way to hunt as far as I'm concerned. I don't have a problem with actively tracking game instead of sitting in a stand all day. But once it comes down to taking the shot, that should be the end of the game.
If I could only have one weapon, I think it would be a .223 carbine (I'm fond of the Bushmaster brand, but just about any would do). These are lighter, highly accurate out to 100 yards or more, and high capacity in terms of ammo. Plus the ammo is fairly cheap and abundant (so that you can hunt small game with it), yet powerful enough to take larger game. I'm also fond of .22 caliber for many of the same reasons, but in a defensive capacity I wouldn't wanna bet my life on a rimfire cartridge.
Food for thought, JMHO... <img src="images/graemlins/smile.gif" alt="" />
Ben