I have used PHPNuke for a while now. I have just started using PostNuke as I am devloping a PN site for a client.
PostNuke has a definate advantage becuase it has many devlopers. And many module makers are dropping PHPNuke.
The devloper of PHPNuke is now the sole devoloper, he does surprise the community with some cool features PHPNuke 5.5 looks promising. But the modules that are now available for PostNuke make it a better choice in my opinion.
If you would like more detailed info feel free to drop me a pm.
