Not sure I'd trust them for self-defense. They're cool, but they tend not to feed well in pumps. A SxS or OU is not a great idea to get into a skirmish with. He with more ammo tends to win a fight that continues past the first 3 shots.
Whether to use the shorty rounds would depend on your own personal setup and how well it functions for you.
For me, the rule is that shotguns are for birds, pistols are for fighting my way to a carbine. Rifles are for hunting - everything.
Here's a good vid on ammo capacity. Yes, he's a cop and thus faces a different type of threat, but I've seen the trend in lots of self-defense shootings too.
