Obviously standing in line for a different line or going to a kiosk is a no-brainer ... and you wouldn't want to spend a lot of time at the kiosk just refreshing if you have the opportunity to do something else in the park.
But it would be interesting to do a speed test to see which is faster, if we're timing based on refreshing the app versus clicking the back button a couple of times to return to the time selection. I'd expect the kiosk to have a quicker connection to the data and not rely on mobile data or general park wifi, although I don't know that for certain.
I generally use the kiosk only for the fifth (and on) FastPass selections - that's still the only way to get those, right?