For defense, parts, durability, dependability and ease of ownership the AR should be fine. (If you want to shoot larger animals, get a .308.) The DDM4 should be fine, or just about any good quality AR like Colt, Bravo Company, Palmeto, S&W, to name a few. Also to be considered are the shotgun and handgun for carry and home defense... in addition to the AR. For durability get a chrome lined barrel, and for accuracy a stainless steel (for those elusive brain stem shots). What sets the ARs apart are the manufacturing tolerances and quality testing. Else there isn't that much difference... the mil spec design is the gun. Penetration might be an issue in a house. The 5.56 won't hardly penetrate hardwall without disintegrating while most hand gun calibers will penetrate. BTW, there is no excuse for not cleaning and lubing. You can get a AR grip that has a compartment for a cleaning kit and oil, so it will always be available for those short pauses while the zombies regroup. =o)