Holy cow, if the njacra is cheaper I would zdeffinately recomend it. Make sure its in good shape. I htink that perhaps yoru hobie owner is a little too proud of his boat. It does of course depend on what your looking for, but that nacra will be more stable, and deffinately faster. If your a bran-new sailor it may be a little overpowering if you have no one to teach you. The 5.7 is a great boat, and with no daggers, it really is stripped to its most simple. Like I said I will leave that hobie 18 like it is standing still.