There is no single-best Perl distribution. Vanilla Perl (relocatable, redistributable Perl), and it's more-developer-friendly Strawberry Perl have significant potential.
However, there is a very good reason why ActivePerl is so very popular. The advantages mostly come in the form of ease of deployment for your end users (no compiler necessary to use their package manager, PPM). The ActiveState PDK (Perl Development Kit) is also a very nice way to pack a complete Windows binary that doesn't require any Perl to be installed on the user's machine.
Unfortunately, many very nice CPAN modules (like the Perl bindings for OpenSSL) are not available via ActiveState's repository.
Like most things, you should make your selection based on which distribution best meets your needs.