You can certainly use IIS if you wish. However, IIS alone will only allow you to server html or ASP pages. To develop using PHP and mySQL, you will need to download the PHP application server, then manually configure IIS. you will also need to download and install the MySQL server.
XAMPP is an all inclusive simple installation. I usually find it takes longer to download XAMPP than it does to install it.
Given the choice of configuring IIS or installing XAMPP, i would recommend XAMPP. With IIS, you will end up having to get you hands dirty to configure PHP support.