I agree that the pump makes the most sense for home defense for the same reason I use a revolver instead of a semi for a home defense pistol--they're not exactly idiot proof, but they're close, and I'd rather any malfunction be squarely my fault than it be the fault of mechanical failure. I trust myself more than I trust any semi-autos that I could afford. being a student I'm confined to a Chinese 870 copy, a gun that has survived almost 10,000 rounds so far and is still going strong. I've practiced with it in multiple configurations on the trap range, shooting from the hip, calling for the bird when the shells were not loaded but in the butt sleeve, and I have become confident that I can run it quick and effective enough to get the job done for HD. I especially like the ease of which you can switch different shells out of a pump, as your left hand can support the gun while working the action at the same time your right hand switches the shells out--much quicker than with any semis I've handled. I also think the pump gun has one of the most ingenious built in safety devices with the slide lock, which people are always confused by if they've never handled one. I usually keep my gun slide locked and unloaded with a full butt sleeve of buck shot and sidesaddle of slugs. I've gotten to the point where it almost doesn't make any difference if the gun were loaded or not, I can still get the first shot off in the same amount of time.
For hunting or real competition, you can't beat the allure of a break action gun.