Having the right rounds in your pistol is secondary. Your PRIMARY focus should be MARKSMANSHIP and nothing but! You can have standard ball ammunition loaded in a .22 and 'get the job done' with a single round and proper marksmanship. Having said that, I wouldn't recommend keeping the ol' Ruger Mk1 as a primary home defense pistol. If you have a short-barreled pistol (that loses a LOT of velocity with regular rounds), I would recommend ammo designed for short barrels that a few manufacturers have put out there.
Interesting article on the subject:
http://www.handgunsmag.com/ammunition/pocket_dynomite/
More important than ammo: MARKSMANSHIP. How many of you practice the Mozambique Drill with 3" x 5" cards on a human silhouette target? Can you do it under all lighting conditions and/or after sprinting 20 yards then doing 10 pushups (to stimulate the ol' ticker)? If you're physically able, then I would suggest practicing that. Walk before you run (literally). Learn proper marksmanship skills, then add the 'stressors'. You won't learn marksmanship at 3 or 7 yards, though. If you can consistently keep your rounds on a 3" x 5" card at 25 yards, then you're familiar with "proper marksmanship". That's a good start. If you can shoot at 25 yards, you increase your chances of hitting what you aim at when you're 7 yards away. 3 yards is up close and personal. That's another class entirely and you should take some advanced marksmanship courses for that.
Support your local NRA or military-trained marksmanship instructor and get instruction from a REAL instructor rather than well-meaning Uncle Billy-Joe-Jim-Bob.