A friends website looks pretty old and is running ASP. They will maybe make the change over to PHP.

What are the pros and cons of doing this?

Here is the website so you can check it out.

valuecruises.net

The appearance of your site has very little to do with the server side code that generates it. If your site looks old it isn't ASP's fault and switching to PHP won't make it look new.

As far as the pros and cons go, the most important thing to consider is whether or not you or someone you work with can develop and manage a PHP site as opposed to an ASP site. In the end, there isn't a whole lot you can do with PHP that you can't do with some other language and vise versa.

Number one, by switching to PHP, will let u have proper is Unix environment! Windows servers really sucks. And dont tell me they are not.
.Net is pretty cool but I can see u have ASP so I would switch to PHP 100%.
Of course there is probably nothing that one language can do and the other one is not.
Saying that PHP is faster might be wrong, but Unix is faster! thats what makes PHP faster.