I think few juries are going to understand the difference and it simply doesn't brief well to the lay person.
it gets to court any good defense attorney is going to be able to kill the weapon issue as it is irrelevant if the weapon was legally owned.
If they are going to try and hang you over using a SBS then they would probably have done the same had you used an 18" shotgun. It all depends on where you live. For example if you lived in Bloomberg's new York you'd probably face charges for shooting a burglar with a BB pistol.
If someone can dismember a burglar with a sword and not face charges, I don't think a NFA weapon is going to have too much difficulty.
Man Kills Burglar with Samurai Sword