Hyphens are for quick, sudden breaks. "..." is for short pauses. Depends how you imagine it sounding in your head.
What he/she said. You read those things two different ways, and although I don't know a lot about stutters in real life, I would imagine people with stutters stutter differently.
For what it's worth, though, while I recall seeing the dashes to imply a stutter in books I've read, I don't think I've ever seen the "..." done. That doesn't mean you shouldn't do it though.