Aside from what my host can cope with, is there any reason you'd use ASP over a CGI script? Can anyone point me towards a source that desscribes the difference between these two methods in respect to emailing online forms?
ASP and PHP are similar BUT ASP is primarily used with Windows Servers and PHP is primarily used with UNIX/LINUX Servers.
CGI is a little different. it's NOT a programming language but a method (I use that loosly). The programming language used with CGI can be Perl, C, Java and others. The most widely used for small applications is Perl.
So the first thing you need to determine is what type of server is being used. If it's Window, the choice is easy; ASP. If it's UNIX, the easiest is probably PHP (althought that's debatable)