I've only sailed the Aussie Blades and haven't seen a VWM blade in the flesh. So I don't know about all the differences. I know the decks and beams are different. The FCA Blade has more rounded decks, and no trap tracks on the inner gunwale (lace the trap to bolts on the boat instead). The beams are a D shaped tube with a built in track, and at a guess 2/3 the size of the viper's. Under the water I think the differences are minimal.

I'll get some photos this weekend and post soon.

Maybe someone that has been to the global challenges, and seen the two boats side by side will be able to explain the differences.