If you are looking for home defense (HD) the statement any round will work is relatively true, especially when compared to pistol ammo. But, having said that, some rounds tend to work better than others, and I would want as many things in my corner as possible if I actually have to resort to the AR in the home.
I know there's a belief M193 (Military 55G FMJ) and it's XM counterpart "tumble" in the human body, but the truth is that's a random event as we learned the hard way in Nam. The reality is the round will often travel through a human without much disruption. That leaves a very small entry and exit wound with a limited permanent cavity and almost no temporary cavity. In other words, unless you get a central nervous system (CNS) hit your target may very well continue whatever it was you were trying to get them to stop. In my mind this makes the FMJ less than optimum for HD. After all, time is something you don't have on your side in the typical HD scenario. The majority of engagements will be within 20 ft, not a lot of time/space for mistakes..
If you reload, the Barnes options open up very fast in the human body and leave large (for the caliber) permanent and temporary cavities.
Many folks like the frangible rounds, I'm not that impressed with them. There have been enough cases of them wasting their energy before they enter deep enough into the body to get a CNS hit or travel through critical organs. Some will quote the protection against over penetration (OP), but that too has been brought into question recently. There's also a potential argument that OP is overstated, but that's for a different thread
Many 223 hunting rounds with soft point bullets will work but they have some negatives too. The biggest one is fouling of the feed ramps and the associated deformation of the bullet. The deformation of the bullet doesn't concern me that much for HD since accuracy is not a concern. After all, the target is withing 20 ft. A round transitioning from 2 MOA to 4 or 5 MOA isn't really a problem. But there is a non-negligible possibility of a failure to feed, and that could be deadly... clearing a FTF when my adversary is within spitting distance doesn't sound like fun. If that happens, my rifle just became an expensive club...a pretty effective club, but I still would have preferred it went bang.
Speer Gold Dot is a very efficient HD round and probably one of the best out there, but the cost is a little too high for my blood.
XMS223SP1 is a very good HD round for the AR-15. It's a soft point, but it has more copper around it than the typical hunting round so the chance of fouling the ramps is greatly reduced, but in ballistic tests (out of a 16 in AR-15) it performed excellently. It uses the Fusion 62gr bonded bullet and the test results showed it to be exactly as effective as the Gold Dot offering, at considerably less cost. This is the round I would suggest you go with.
Something to keep in mind with HD ammo is you should run several boxes through your rifle before you settle on a given round. Personally, I wouldn't trust my family to any round until I fired at least 200+ without a failure.
AR's, being a gas operated system employing a Direct Impingement approach they can be very sensitive to things like absolute pressure and dwell time. Basically, some rounds just won't operate every AR. Run enough rounds through your weapon that you trust those rounds before you bet your life on them.
Good luck in your hunt for a HD round...and may you never actually need it!