Personally I would go with python base on my pass experience. They both can pretty much do everything the other can do, but Python's code will most likely be shorter and more organized than Perl. Which means Python is easier to read and maintain when you want to modify it, and Perl is fine until you go up to a few hundred lines, the code will start to get messy.
I guess if it is a small project you could go with either, but if something big then I would suggest Python just to make your life easier. =)
(edit: Ops. Didn't noticed the post was a year ago)
It depends. Python has a simple and elegant base language while the power resides in its library. On the other hand, Perl tends to be cryptic and hard to read. If you are a decent programmer you will write more eligible code than a bad one, but Perl's power is reflected in its rather complex syntax and many operator symbols
Well, both are almost the same - but I would still prefer Perl - just because it is more cryptic and looks complicated (which in fact it is not). Also, perl will integrate on the PHP servers better and easier.