How is Nginx better than IIS?

Question

Nginx

We have a large set of React SinglePage applications with a .NET backend hosted on IIS.
For developers and for testing, we have chosen such a scheme that we have two virtual machines, one Windows Server 2016 with IIS for the backend and one Linux with Nginx as a proxy and a web server for statics.
Nginx is used as a single entry point for the end user - HTTPS is configured on it, logging is configured, routing is configured - we analyze the request URL and decide on it - redirect the request to the backend server or give static files directly from Nginx.
Now there is a question of expansion at the Customer.
The customer strongly wants to abandon a separate virtual machine with Nginx, arguing that everything can be done in IIS. By and large, this is true, but we would very much like to leave our scheme.
Tell me, please, weighty arguments can be made in favor of a bundle of Nginx + IIS instead of one IIS.

Answer 1

Firstly, Nginx has very high performance with very low demands on server resources. In your scheme, a hundred thousand simultaneous requests for statics will be processed in a reasonable time and will not affect the performance of the backend in any way. In the customer's scheme, both the return of statics and back will start to slow down, it is possible that the server will stop responding to requests altogether.
Secondly, Nginx is very reliable and secure. Not least because in the basic configuration it is as simple as a brick. Ensuring the same level of hack resistance for IIS requires significantly more admin skills and effort.

Answer 2

Read the spa hosting guide, maybe http.sys is right for you.