Well, I believe in many cases the "fastest response" hardware is the best solution. Say, you want to count pulses from a 10.000 RPM, high-resolution encoder. Either you implement some CPU that can handle way more than 1MHZ pulses,

You don't get it, do you?

It is totally irrelevant how fast your encoder run, when it stop on a border you will get extremely fast pulses regardless of the encoder speed

Erik