A manual feed system offers traditional, hands-on control, while a threaded cross feed system provides enhanced precision and consistency, reducing manual effort and expanding the range of possible operations. The manual feed is basically "it goes where you push it" and you are in control of the router placement. This is the more ‘traditional’ router sled style of control where you’re basically emulating a rowing machine going back and forth across the width of the project to plane it down. The threaded cross feed units have a threaded rod that you can pin the router to in order to control the placement across the width of the unit. This allows you to have consistent width passes parallel to the grain or long axis of the mill. This gives a much better surface finish (which means less sanding), plus none of us have 4ft long arms to reach across the entire width in one go. It also opens up the ability to handle inlays, edge jointing, equally spaced fluting, and other straight line routing operations since you can control the router's position with a simple hand crank. Effectively turns the unit into a router table flipped upside down.