One may perform better than the other, but there's not really an easy way to predict which would perform better. Probably if you are running mod_php on Apache, then PHP will perform better, but thats not really a guarantee.
Like RelicHOST said, it really comes down to which ever you are more comfortable with.
Personally, I find perl to be a rather dependent, ugly, overbearing language. PHP is where it's at for me, though I've been working with C for quite some time, so that's probably where that comes from.
perl requires specific permissions usually to be set, so it's a bit more complicated to work with, while php can work in anything usually, providing php is compiled into the server.
PHP is by far a more widely used language. There are programmers in both languages that can do magic, but certainly there is a lot more available in PHP including scripts, frameworks, tools, programmers, etc.
If you're doing web stuff stick with php, since perl is almost dead as a web development language. If, on the other hand, you're doing systems administration (moving and editing files etc.) perl is the best language for linux hands down.
Perl is hardly dead (or practically dead) and is used by millions of people each day and permissions are not that complicated either (you do the same for PHP scripts, even in the Apache API). Use whatever you like better, as neither will be going away or have their development cease. So either are fine. The rest of the differences you hear is all but really opinions.