The answer to 'backflow preventer vs' is that a backflow preventer is a plumbing device that prevents water from flowing backward into the potable water supply, while a check valve is a simpler device that allows water to flow in only one direction. Backflow preventers are required by code in many areas to protect the public water supply, while check valves are more commonly used in private plumbing systems.
Backflow preventers are more complex and typically more expensive than check valves, but they provide a higher level of protection against contamination. They are often required for commercial and industrial buildings, as well as in homes with irrigation systems or other potential sources of backflow. Check valves are simpler and less expensive, but they may not provide the same level of protection as a backflow preventer.