There is a big difference between a motorcycle oil and a car oil.
The lubricant for cars, is just that, a lubricant. It's only purpose is to provide lubrication to the parts so they face minimum friction, they have friction modifiers added to reduce friction. Cars have dry clutch, so no oil there. Cars have separate transmission, with it's own oil. Cars are water cooled, radiator, coolant and stuff.
Motor bike oil has to do all of the above jobs. Lubricate the parts, but the clutch is wet with the same oil, so it can not be of minimum friction, because that will make the clutch slip (not immediately but it will happen). The transmission uses the same oil, where it is faced with more forces acting to break it down, compared to a car. And it is used as a coolant in the engine as well.
When one changes to a car lubricant it feels like the engine is running smooth, which it is because of friction modifiers, but these same friction modifiers will stick to the clutch plates and make it slip.
Stick with API SG as recommended by the motorbike manufacturer. Go with the brand/manufacturer of your choice, but stick with API SG for your motorbike.
If you want more info just google for "oil difference motorbike car"