In reply to Presley Whippet:
Isn't it clear by now, with all these endless discussions, that the two types of devices - Grigri and ATC-type belayers - have different pros and cons, so the type of climbing dictates which is the more appropriate to use.
As far as I can see, a majority of sport climbers favour the GriGri, whereas the vast majority of trad climbers favour ATC-type devices - both for good reasons.