Php and asp.net

Hi all,

Can u plz help me in deciding a web language for my final graduation project ...
it is a web based monitoring system not more than huge relational database ,,,,
I am really confused ,I can't decide between php and asp.net
actually i have some background on php...but nothing on (.Net) especially asp.net...
so can u plz give me ur advice..and why??
I would like to know more features about both languages..

Thanx alot