PGStaff will likely chime in (and when he does, PlayballTX, know that he is founder and CEO of PG). Most all of the local showcases are the same with the exceptions of location and class that you noted.
Note that the showcases can be local, regional and national, with the talent pool increasingly better at each.
The showcases that tend to be significantly different are the National and Jr. National showcases which are the truly premier showcase events that tend to have the absolute top players of the class. Here you see a good measure of best against best. Also, the "uncommitted" showcases are just that, all participants have yet to commit to a school, so college RC's can take particular interest of seeing a lot to shop at these events.
I'm probably doing a great disservice with the brief description, so apologies to Jerry in advance when he chimes in, but that's my observation in a nutshell.