I can. Obviously I don't know the exact numbers of the radios I have used but I have noticed the differences. Spektrum sucked, M8 was very good, M11 was slightly better still.

That being said, I really can't tell much if any difference running dirt. But 1/8th onroad and especially 1/12th, yes it matters.

Want to see the difference of a few ms for yourself? Get a wired Xbox controller and one of those golf games where you have to hit the button at a specific time to hit the shot (or any other game like that). Play it with the wired controller until you have mastered it, then switch to wireless. You will suck at it for a while.