Site creation with Azure Runbooks? Never heard of it!
With AR you can create coder units based on PowerShell or other languages. Modules like the PNP-Framework, SPO etc. can be installed with one click. You can pass parameters to your scripts and the best thing is that you can trigger the execution of a script via Flow. This gives you the ability to create a library of useful scripts that can run directly from a Flow. Runbooks can also be scheduled by a timer job.
Why should I create sites via Azure Runbooks?
When it comes to the structure of sites and groups in your organization you will run into the following dilemma: You create groups and sites and the naming schema will cause confusion after a while. Just think of two departments creating a group called "profit center". When you click on the little plus icon in SharePoint you are free to give your site a name. There is no form that asks you for settings and parameters resulting in a individual naming convention for your groups and sites. And there is also no way to create a customized creation workflow.
Microsoft just already released a new feature to add a prefix of suffix to a group when it's created. But this doesn't work for communication sites and other resourcesm, and with your Runbook scripts you can also deploy settings for sharing, adding entries to the hub-site navigation, create and fill pages with webparts and so much more. Think your your Runbook as the swiss army knife of scripting.
With this method you gain more control over your site and group structures avoiding the uncontrolled sprawl. Just think of how your information landscape will look in 5 years. And you can build a library of scheduled jobs to maintain your Office 365 environment.