Gear Ball takes the Ball tip and extends the Xtreme Dash gearing all the way down around it, so the teeth themselves reach the stadium surface. Movement is recognisably Ball-like — the same wide, controllable circles — but a little more aggressive, especially on an angled launch where the gears bite the floor. The extended teeth also grip the X-Celerator rail far more readily and accelerate harder off it, which is the whole point of the part.
That is also its problem. The gears drag, costing stamina against plain Ball, and the sudden bursts of speed they produce cut both ways: self-knock-outs go up, and a tilting Gear Ball combo can behave erratically, jolting forward in short unpredictable spurts. Nothing about the design adds burst resistance to compensate.
The consensus is that Gear Ball is outclassed by the part it is derived from. It has a narrow use in stamina-versus-stamina matchups where the extra dash occasionally steals a knock-out, but competitive players almost universally substitute plain Ball.