Microfiber bonnets / pads / cloth are not as absorbent as cotton. They will not absorb as much water.
Because of the very narrow diameter and the shape of the fiber, microfiber has a lot of surface area to trap and hold fine particulate soils. A portion of the fiber is oleophillic or oil-loving. So it also does well on holding and trapping oily soils.
So comapred to cotton, cotton wins on water and soils disolved in water. Microfiber will remove more dry soils and more oily soils.