According to what I have read, a PR system is fundamentally the same as a ported system, except it is more easily tuned by mass loading the PR instead of changing port dimensions. Also it avoids the port "wind" noise problem.
One interesting variation is to use a full driver (including magnet and voice coil) instead of a PR. Then you can tweek the system with inductors and capacitors across the coil, as well as by mass loading.
A final version, that I have played with is to actively drive the driver that functioning as a PR with a separate SW power amp that has frequency and phase control. If I had to give this scheme a name I would call it "Active Damped".
But, when all is said and done, my preference is for a Planar (or open baffle) system, with a sealed subwoofer.