If my amateur science memory serves me correctly, it's all about the difference in width between the two boats. Basically, you can build more pressure on the sail, which in turn will move you faster. When the Bravo starts to tip up, you will still be able to keep the Wave level. The level boat has more pressure on the sails, and more pressure (actually it would be called lift, but that's only if you can imagine the sail like an airplane wing on it's side) the faster the boat goes.
I'm sure there's someone on this board who can explain it better, but it will probably boil down to that. Unless my amateur science memory is failing me.