As a result of their scientific experiments the Wright Brothers had developed a better aerofoil design. The lower angle of attack of the 1902 glider indicates its superior performance in terms of lift to drag ratio.
< Wilbur and Orville flying the 1901 glider as a kite to test its performance
> Dan Tate and Wilbur Wright flying the 1902 glider, after changes had been made to the aerofoil shape
These images, and many others, can be found on Gary Bradshaw's "To Fly is Everything" web site: http://invention.psychology.msstate.edu/air_main.shtml