As Puhba said lower is faster, because you can make faster steering inputs. With lower angles you never have to take hands of steering wheel to turn more.
I myself used 720, when I got my G25 years ago. I then changed to 540 after noticing that I was giving others a big advantage, because in some situations, I couldn't steer fast enough. 540 is IMO good compromise between feel, accuracy and steering speed.