Hi,
We cannot compare SaaS vs Azure or sorry if I cannot get your question.
For Business Central we have two major options one is Cloud (SaaS) version that is by getting a subscription otherwise (On-Prem) that we can Install locally, or host the DB in azure or docker based installation.
With SaaS security and control is in Microsoft hands. You have access through web or Business central app.
Licensing cost for Business central essentials On-Prem is around 1450 USD per user for one time.
Licensing cost for Business central essential Cloud is 70 USD per month.