If you have a busy site, you won't want to use vanilla Perl CGI. You'll probably want to use the native mod_perl API, or use the CGI interface with Apache::Registry and mod_perl. The difference in speed is significant realtive to standard CGI

I like PHP. I have nothing against it, and use it form time to time, but just like Perl better. Really, there is no real "correct" answer to these questions. It comes down to personal taste. But you know Perl, so maybe that's what you should stick with