I had the pizza burger at DLP back in 1997. And I have to say that the pizza burgers that are served by the local drive-in restaurant here in Ohio are just as good as those served at DLP.
The theming of Pizza Planet at DLP was indeed much nicer than WDW, but that is probably due to the fact that WDW's version was shoehorned into an existing building and that DLP's version was built from the ground up.