It depends on whether or not you're going to be receiving IPNs from PayPal that aren't the result of PayPal WPP API calls. The PayPal modules specifies what IPN URL to use, but if PayPal needs to send out generic IPNs for your account it will use the IPN URL specified in your PayPal profile settings.
I am not sure if I am going to need that or not. I sell digital products. I just need to be sure that after sucessful payment UC gives the file to the user.