  We search fora dichotomy/bimodality between Radio Loud (RL) and Radio Quiet
(RQ) Type 1 Active Galactic Nuclei (AGN). We examine several samples of SDSS
QSOs with high S/N optical spectra and matching FIRST/NVSS radio observations.
We use the radio data to identify the weakest RL sources with FRII structure to
define a RL/RQ boundary which corresponds to log L$_{1.4GHz}$=31.6 ergs
s$^{-1}$ Hz$^{-1}$. We measure properties of broad line H$\beta$ and FeII
emission to define the optical plane of a 4DE1 spectroscopic diagnostic space.
The RL quasars occupy a much more restricted domain in this optical plane
compared to the RQ sources, which a 2D Kolmogorov-Smirnov test finds to be
highly significant. This tells us that the range of BLR kinematics and
structure for RL sources is more restricted than for the RQ QSOs, which
supports the notion of dichotomy. FRII and CD RL sources also show significant
4DE1 domain differences that likely reflect differences in line of sight
orientation (inclined vs. face-on respectively) for these two classes. The
possibility of a distinct Radio Intermediate (RI) population between RQ and RL
source is disfavored because a 4DE1 diagnostic space comparison shows no
difference between RI and RQ sources. We show that searches for dichotomy in
radio vs. bolometric luminosity diagrams will yield ambiguous results mainly
because in a reasonably complete sample the radio brightest RQ sources will be
numerous enough to blur the gap between RQ and RL sources. Within resolution
constraints of NVSS and FIRST we find no FRI sources among the broad line
quasar population.
