I am not sure about the performance difference - might be interesting to investigate.

However, one important thing is the use of nginx as a reverse proxy for urls with different domains/servernames but resolving to the same IP address.

Basically you want nodejs to serve 1 application - uWS makes it faster - but you want nginx to serve multiple applications from a single point of access.

It's correct that you don't need Nginx at all.

You don't lose any functionality (there isn't anything special that Nginx does that uWS doesn't).

I also migrated from using Nginx+Express to just uWS about a year ago, managing many servers at once.

It works flawlessly, only challenge I had in my case was to make uWS handle SSL for multiple domains + wildcards through a single router, but it worked well at the end and was worth it.

I use a single uWS server to manage all my web applications, which makes this easier, and for cases where I needed a separate server I made a simple proxy function built into my uWS router.

Removing Nginx can make your setup simpler, less bloated and also faster by a small bit.

Performance-wise you will most likely see a small improvement since a proxy is just an extra step. The difference won't be significant but it'l be there, so unless you need Nginx for other things, I'd say go for it.

I also just realized that this question is over 5 years old.

Over these 5 years, there is only one reason why Nginx is needed, it is HTTP 2 and HTTP 3, uWS works only on HTTP 1.1, this means that all your requests in 1 connection are executed sequentially, without multiplexing, this is important for performance.