Lead and iron pipes differ significantly in their properties. Lead pipes are more malleable and flexible, while iron pipes are stronger and more durable. Iron pipes are more resistant to corrosion, making them suitable for outdoor use, but lead pipes are more toxic and can pose health risks. In terms of applications, lead pipes were historically used in plumbing but have been largely replaced by iron pipes due to health concerns. Iron pipes are widely used in construction, manufacturing, and plumbing systems.