I'd pick the boat that is strongest in your area.

Up here in the Pacific Northwest that would be the Hobie Tiger. There are several Nacra's up in Vancouver, but they have never traveled with any seriousness.
We've got a full year planned for the Hobie One Design Regattas, and we'll go to a couple F18 events too.
Our class will be racing with the entire range of production years. It will come down to sailor skill more than new boat.