It's interesting how people have different experiences, because my ackies are the most prone to biting (other than feeding response), out of argus, gouldii, and peachies.
All things must be taken in context though, the ackies are the most handleable of mine, mostly because of size. But once they get pissed, which admittedly isn't often, they are the first to bite, my argus will do tons of hissing, tail whipping and posturing before biting. The peachies and argus do warning lunges, but have not ever connected, all bluff IMO. My argus are still young, and comparably small (2.5') so, perhaps my opinion will change in time.
Both argus and ackies are fun monitors. But I'm probably slightly on the weird side, as I enjoy 'spirited' monitors.
--Robert