  We compare three semi-microscopic theories to the first data on particle
production in central Au+Au collisions taken at RHIC by the PHOBOS
collaboration as well as to existing data on central Pb+Pb collisions taken at
the SPS by the NA49 collaboration. LEXUS represents the SPS data quite well but
not the RHIC data, whereas the wounded nucleon model does the opposite. The
collective tube model fails to describe any of the data. This suggests a
transition in the dynamics of particle production between \sqrt{s} = 17 and 56
A GeV as one goes from the SPS to RHIC.
