How does vert.x compare to spring?

Vert.x and Spring framework are like Apples and Oranges which can't be compared. A proper comparison would be between Vert.x and WebFlux (part of Spring 5 - https://docs.spring.io/spring-framework/docs/5.0.0.BUILD-SNAPSHOT/spring-framework-reference/html/web-reactive.html ). I'm assuming you are talking about the Spring framework and not Spring Boot.

thanks this is very helpful