PHP 5 performance compared to PHP 4?

Hi all,

I think this belongs on php evangelism.
I have earned enough trust to convince the company to install php on our 
IIS server. I would like to see some performace comparison between PHP 5 
and PHP 4, if possible under both Linux and Windows. Can Include 
comparisons to  ASP etc too, but I am more concerned in knowing whether 
the upgrade from version 4 to version 5 will be worthwhile. Do you have 
some numbers or URLs to share?