Using braided lines for bobber fishing will give you a lot better flotation of your line because the line grease stays on a lot longer than with monofilament lines. This is important because you want to keep the line above your bobber floating on the surface so you can keep it mended and get a quick hookset when your bobber goes down. If the line sinks you cant mend it and you get a big bow in the line, creating too much slack. Also less stretch.