The Nacra 450 is a little small for two adults - it's really more of a kid's boat. I think the Wave is probably the better choice - a great boat for fooling around with and easier to sell if you later want something more exciting.
The point about resale makes really good sense but as I was standing next to the 450 yesterday, I sure didn't get the feeling of a kid's boat. The 450 is longer and wider than the wave. (and maybe also carries more sail).
