A rudder makes a plane more fun to fly IMO. This past summer I got into some super strong thermals down low and had my glider hooked so tight I know it couldnt of happened without my rudder. Im sure I could have been flatter and much more efficient but Im into this for kicks as well and the darn thing was super cool to see literary climbing like crazy in about a 10 ft radius
Concerning performance. I believe rudderless has a advantage for launch ,sink rate but down low [below 30 ft] rudders rule.