Let's see....any handgun round OR a charge of buckshot or rifled slug out of a 12 ga shotgun? Which one would be excessive force?
Lumpy is exactly right. The entire issue is whether or not the homeowner is justified in using deadly force at all. If the use of deadly force is legally justified, what the homeowner uses would only be a legal issue if the weapon itself was illegal (i.e., unlicensed full auto, SBR, sawed-off, grenade launcher, etc.). Under NC law, violation of a "public safety" statute, which covers some firearms laws, such as carrying a concealed weapon, or negligently discharging a firearm (i.e., no backstop), would support a charge of involuntary manslaughter. But neither of these statutes would apply in a home-defense situation.
I would not put it past some politically correct, ambitious District Attorneys to try to show that the homeowner had a "killer" mindset because he had a customized handgun, or an "evil assault weapon" or had (horror of horrors) actually received training with his firearm. But juries in NC tend to be rather conservative on firearms issues, so most DAs don't even bother to raise such issues.
So it's not worth worrying about WHAT you use for self-defense, rather you should know your state's laws concerning use of deadly force well enough to know WHEN you are justified in shooting. After that, it's just a matter of marksmanship.....