  Gamma-ray bursts (GRBs), observed to redshift $z=9.4$, are potential probes
of the largely unexplored $z\sim 2.7-9.4$ part of the early Universe. Thus,
finding relevant relations among GRB physical properties is crucial. We find
that the Platinum GRB data compilation, with 50 long GRBs (with relatively flat
plateaus and no flares) in the redshift range $0.553 \leq z \leq 5.0$, and the
LGRB95 data compilation, with 95 long GRBs in $0.297 \leq z \leq 9.4$, as well
as the 145 GRB combination of the two, strongly favor the three-dimensional
(3D) fundamental plane (Dainotti) correlation relation (between the peak prompt
lumininosity, the luminosity at the end of the plateau emission, and its rest
frame duration) over the two-dimensional one (between the luminosity at the end
of the plateau emission and its duration). The 3D Dainotti correlations in the
three data sets are standardizable. We find that while LGRB95 data have
$\sim50$% larger intrinsic scatter parameter values than the better-quality
Platinum data, they provide somewhat tighter constraints on cosmological-model
and GRB-correlation parameters, perhaps solely due to the larger number of data
points, 95 versus 50. This suggests that when compiling GRB data for the
purpose of constraining cosmological parameters, given the quality of current
GRB data, intrinsic scatter parameter reduction must be balanced against
reduced sample size.
