Updating old/failed pages - reuse old URL or 301 redirect to new?

Hey, if we’re updating a page (4+ years old) that hasn’t ranked well for the keywords we wanted, and we’re doing a major overhaul while still targeting the same keywords, what’s the best SEO approach? I'm wondering if they have been stagnant for so long that it's better to create new URLs for these and 301 redirect the old ones? Or is it better to reuse the existing URLs?