what is the advantage of using web_custom_request (http/html protocol) over webservice protocol LR

Can anyone please explain what is the advantage of testing a API/webservice using webservices protocol over the http/html protocol [ web_custom_request ( ) ].

In my past to load test the webservice , i built my scripts using web_custom_request ( ). Recently my new project has asked me to confirm can we test the API testing using Load Runner. 

If we can do the API / webservice testing using the HTTP/HTML protocol with the web_custim_request ( ) function then we dont have to upgrade our license from web to web2.

Thanks,

John.