The PPM repositories are not static and are generally up-to-date. Some issues exist with some modules in getting them to compile on Windows. And obviously some won't work on Windows at all for a variety of reasons, the same way there are Windows-specific modules that might end up on CPAN, but won't work on Unix/Linux. But I have rarely encountered a newer version of a module on CPAN that didn't make it into the Activestate, Trouchelle, Bribes de Perl, or U of Winnipeg repositories before long.

Also, the newer versions of PPM will manage modules that you have installed via the CPAN or CPANPLUS shells, which the OP might be interested in checking out.

--marmot

Update: Changed PPM repository URL's to human-readable destinations.