Speaking--as usual--with no actual factual support for my opinion, I'd say that Gozilla predates Mozilla: it's a more likely coinage, having an easily recognizable connection. Mozilla would depend upon the prior existence of Gozilla to have any catch to it: Gozilla implies a monster way of getting someplace; Mozilla, after Gozilla, implies even faster than Gozilla. But, as I say, never having heard of either before, this is just idle speculation, that for which I have become famous...

--seed