glDrawElements or glDrawArrays?

Which is faster and why is it ???

I’d thank that you download my opengl program from my page:

I’d like you to test my program, I think it is slow, but I’d like your opinion.

Its implementation dependant. You could say that in theory glDrawArrays should be slightly faster since you dont have to pass indices like in glDrawElements, BUT you could also say glDrawElements is faster if you share vertices in the array, since they can be cached more easilly in the OpenGL driver, and glDrawArrays may have to transform shared vertices multiple times.
I prefer drawelements, because of it’s more flexible.