It's pretty funny how similar they are. The Flood spread until they can form a gravemind, and then they're much more motivated and organized. The Necromorphs spread until they've infected a planet to make a brethren moon.
I think the fairest situation would be to infect one planet with a sample of Flood spore, and place a marker on another planet. Since the marker is essentially a proto-gravemind, I'd say the necros have an early advantage. However, the Flood spreads significantly faster, and with the ability to absorb the intelligence of the host, I think would be a bigger threat in the long run.
English
-
[quote]I think the fairest situation would be to infect one planet with a sample of Flood spore, and place a marker on another planet[/quote] OR put them both on the same planet (opposite hemispheres) and see who prevails as the superior race by either assimilating the ENTIRE planet (including the opposing parasite) or getting off-planet to infect other worlds. I'd pay money to see a real-time simulation of that.