Actually, the question of whether whether you want to consider them
different genera in addition is entirely left to your (yes, your)
taste is entirely left to your (yes, your) taste. It's clear that
David prefers to think of genera as _wholly_ arbitrary, but there are
plenty of workers who disagree. We should all remember that
vertebrate palaeontology, and perhaps dinosaur palaeontology in
particular, is very avant garde in this respect -- start talking
about genera being purely arbitrary on, say, an extant entomology
mailing list if you don't believe me.