I figure there are MANY good horses out there that aren't N/H (or H/H). I'd rather find one of them so I don't have to always have that anxiety of "what if today there's an attack?". I wouldn't be able to relax.

I know people say with proper care/feeding/maintenance, you can mitigate the likelihood of an attack in an N/H horse but I've also seen people say that's hogwash.

Just because the horse has never had a (visible, obvious) attack before doesn't mean that won't change. It's kind of like going to the casino: just because you're on a winning streak doesn't mean you won't lose it all with the next roll of the dice.