The router has an advantage when it comes to working at a greater distance from the edge of the workpiece. The dimensions of the router table are a limiting factor here.
Working on the router table is safer and more precise; with the mobile hand router you are more flexible.
Short, thin and narrow workpieces are better machined on the router table. Large panels are better machined with the hand router.
Serial routing with the same dimensions is easier and faster on the router table with its stops to which you can attach appropriate fixtures. If you only need to make a single routing, it is often quicker and easier to use the hand router.