We perform a detailed analysis of the next-to-minimal supersymmetric standard
model (NMSSM), imposing the constraints of two-loop gauge coupling unification,
universal soft supersymmetry breaking and the correct pattern of electroweak
symmetry breaking. We compare our results with those for the minimal
supersymmetric standard model (MSSM) using closely related techniques and, as
far as possible, a common set of input and output variables. In general, in the
constrained NMSSM, there are much stronger correlations between parameters than
in the constrained MSSM, and we map out the allowed parameter space. We also
give a detailed discussion of how to resolve the two models experimentally,
concentrating primarily on the prospects at LEPII.Comment: 76 pages, latex, no macros, uuencoded figures included separately.
This version (to appear in Phys. Rev. D) contains various minor change