Adding a web application vs creating a new website

In our project we are creating new WebAPIs and we already have a Website - ABC that runs in IIS 7.0. The new WebAPIs are independent services as such. These are intended to be used by different components in the solution and by external clients as well. Few of these WebAPIs can be used heavily. There are 3 ways for me to host the new WebAPIs -

1. As a Virtual Directory in existing Website ABC
2. As a web application in existing Website ABC
3. As a new Website

I overruled the first option due to common Application pool restriction.

Now whether these WebAPIs should be added as web application to the existing website ABC OR should they be created as new websites each if they are on the same machine?