If you really wanted to learn to defend your home with a sword, buy a rapier and learn fencing, it would serve you much better in narrow hallways.
Matthew, Iaido is the art of the katana draw. You draw and cut in a single move. Kendo is Japanese fencing, you wear armor and actually hit your opponent with a bamboo sword (called a shinai).
I haven't taken either of them, but I would think that Kendo would be more productive normally (building reaction time, relieving stress), but Iaido would be much more useful in a home invasion senario. Kendo is a sport, and as such, is designed for optimum use in the sport against an armored and bladed oponent. While with Iaido, the crook probably won't think of a sheathed sword as much of a threat and you can get that one cut in.