Hapi's philosophy is that configuration is more important than code. This is especially useful for very large teams because it helps developers maintain consistency and reusability throughout their code.
Hapi seems to be made with large applications in mind. The sheer amount of boilerplate code it requires is simply not practical for a small web app. This also means that there are few examples of Hapi applications around for beginners to learn from.
Sails follows the Convention over Configuration philosophy. This is shown even through the CLI that comes with it which quickly and painlessly generates and scaffolds a new project following the conventions already established by the Sails community.