Originally Posted by Kari5
I haven't seen both of them, but this might be a special case (usually OVAs don't come first) because the tv series is much larger and the OVA is somewhat like a pilot(?)?
(I'd like another mod'd opinion on this)
I've watched both and the OVA was quite popular by itself well before the series. It also spawned manga and games based off it so I would be fine with it being either as main.
I think I generally do stuff chronologically if they start off in a OVA/Movie then a series spawns off it the OVA/Movie is still their main as it's the original work. But stuff like episode 0's / pilots / previews I would stick with the series.