Hi!
I've been in the same quest for the coolest language for web programming but I've found that PHP is the best. Anyway, if you know it, there's no need to learn another one. Of course, Python is said to be more object-oriented (although I didn't check, and OOP capabilities of PHP grow as it moves along), it can be used for desktop app development (with appropriate extensions for that, although PHP-GTK serves the same purpose. There's a variety of articles on Devshed if you want to check out its functionality.
I recently read an article comparing many web-oriented scripting languages and Python is said to be slower. Although this is such a relative term...
So far I stayed with PHP, use for two corporate websites I am working on and am pretty happy with it. One can begin to say that JSP for instance is compiled, which makes the code faster, that ASP is compiled too and more reliable, but so much also depends on a good provider and the hardware they use. Plus PHP is supported more widely than anything else. In this respect it's only beaten by Perl.
Zope is built using Python. Check it out too at www.zend.com. I think it's not the fastest one can get, to my thinking.
All the best in your quest,
Stas