Whats better for home defense?

[Barth]

Is a grain like 135 or 165 better than like 185 for home defense so it doesn't penetrate through walls and stuff?

I'm not a big fan of frangible ammo.
But in a thin walled condo, or whatever, something like a Glaser Safety Slug may be worth consideration.

I believe initially United States Federal Air Marshals were using them.
Although I think they have since switched to standard JHP ammo.

Penetration is a result of bullet weight, velocity and design.
Just looking at one aspect is misleading.

As an example;
125 gr 357 Sig is known for outstanding light barrier penetration.
Recommend you look at actual FBI Protocol penetration results to compare specific loads.

A shotgun, with the right ammo, makes for a very effective low penetration home defense weapon.

[Brian Edwards]

When speaking of home defense, a nice OTM bullet in .223Rem or 5.56x45 will always be superior to a handgun round. A lightweight (77grs or less) bullet traveling at a high velocity (2,600 fps or more) simply makes for a better round. It will have rifle type terminal effect (wounding) but because of the fragile construction of an OTM, the lightweight, and high velocity it will indeed tear its self apart in sheetrock and the like.

Note the trend in LE, especially SWAT/ERT/SERT/ESU types, have virtually all gone to weapons that fire the .223Rem or 5.56x45. In the world of liability, they have found they get excellent terminal performance with a much reduced over penetration risk. Here in Dallas, TX, only rarely does DPD Tactical ever break out an MP5, if ever, and shotguns are for breaching only. Everything else is done with Colt ARs. That same reasoning is easily translated to a homeowner that is defending his our her home.

As with any firearm; training from a known entity is crucial.