5 ms = 200hz
2 ms = 500hz
essentially those are the refresh rates that would limit the response time in order for you to notice any artifacts. Consequently, if either monitor is hooked up to a rig that is putting out 60hz video, you won't see any difference.
as far as can human eye notice anything faster or slower, yes a human eye can notice things faster than 8 ms, it depends on the conditions in which an eye has to notice things. But as far as your ability to tell between 5ms and 2ms - human brain has no way of distinguishing even if the eye can.