The PS90 in 5.7x28 is an actual PDW(personal defense weapon)as defined by military standards. Effective tomabout 200 yards as opposed to say 600 yds. It is more maneuverable in close quarters than an M4. It was intended for support staff in the rear. The ballistics if the 5.7 round are pretty much between that of a .223 or 5.56. And a .22 mag. I dont think either would be a bad choice for home defense, but take into consideration your home layout and distance from other living quarters due to penetration of the different rounds. What i do like about the 5.7 is you can mate it with its partner handgun the FiveseveN both from FNH. The FNH products and ammo are more expensive so money may be a factor. If not i would go with the duo PDW and handgun from FNH. You can also look in the AR-57 an AR that is made by Aero Precision in Washington State which comes with a 5.7 upper, and can be changed out to a regular 5.56 upper when so desired. The projectiles are about the same weight as a .22 so over penetration should not be much of a worry.