If white gets to take an entire turn before black starts, then I think
it's appropriate to measure game length in turns, not in moves (if
different).
Though I've seen several double-move Chess variants that restrict white to
a single move on the first turn in an attempt to counteract the first-turn
advantage; have you considered a Chieftain variant that only allows white
to make half the usual number of allowed moves on the first turn?
