Speed for a comparator would mean its reponce time to change in input.
One has to take care of what responce time you need for what change in input step. The responce time would vary for a 1V step input and 5mV step input. One has to design depending on the step voltage input requirment.
Speed of opam would be time it take to give the desired ouput for a input change.Or if the oupput is disturbed , how much rime it take to restore to its original value. Limitied by 3dB bandwidth in closed loop.