Between the GS500F and the Ninja 500r.....
Ninja, a little more power, less comfy, old school looks, good handling.
GS500F, newer styling, more comfy, good handling, decent power.
I have ridden both and bought the Suzuki, for me being 6 ft 200 lbs It fit me just fine and felt more stable and slower speeds. With me on it it will wind out to about 120 but it takes awhile from 100 to 120.