I don't look at it in a technical light, but rather how do you wish to be shaped by the tools you use and create; and the people you interact with and learn from. For example, here's a short list of how I view the choice differential.
Use Perl if:
- primary use unix, BSD, linux
- care about portability and longevity of your work
- prefer master of the language and workflow efficiency
- are familiar with and like the Unixtm philosphy for tools
- believe that a user community exists such that you tend to mastery (i.e., believe that iron sharpens iron)
- see the value of an unbroken linkage to unix wizards of the past
- not only comfortable with, but are actually attracted to the idea of being among a class of remnant working and toiling for the day that Perl will be rediscovered and appreciated
Use Python if:
- primarily use Windows or are agnostic to the OS
- don't care about the longevity or portability of your work
- wish to be a jack o' all trade
- prefer to be part of the herd