For a truck gun, 223. For home and personal defense, either will work. Use the one you have the most confidence in.
Choose a model that fits you and is comfortable to shoot. If it is too long or too short you will not point it naturally. Make sure it is reliable, it has to shoot every time you pull the trigger.
In a defense situation you want your gun to become part of you so you don't have to think about how to shoot it. That takes practice. Lots of practice. If you can't hit your attacker it won't matter what cartridge you have.
You can't fix stupid....however ignorance can be cured through education!