How to argue with ASP people...

I am fairly new to PHP, but I am loving it... I have recently gotten involved in a business venture and I have been using PHP so far... Recently I have taken on a partner, and he is a big ASP guy... I am not totally against ASP, but it would have to be pretty good to get me to switch at this point (PHP seems to do everything I need)... But I will need to convince him of this... What points can I bring up in PHP's favor? In what areas does PHP trounce ASP? -- td