However, here are some of my impressions, in no particular order:
1. Micronaut comes from the team behind Grails, which is built on top of Spring. It is clearly designed to be as familiar as possible for developers with Spring experience.
2. Quarkus comes from the developers behind JBoss (or Wildfly, whatever). It is clearly designed to be as familiar as possible for developers with Java EE experience.
3. If you have experience with neither Spring nor Java EE, then the Micronaut documentation will probably be easier to follow. The Quarkus documentation assumes that you already know a lot about CDI and other Java EE standards, and it mostly focuses on how Quarkus differs from those specs. Their documentation SUCKS at presenting the framework to a fresh audience without all that baggage.
4. On the other hand, Quarkus actually delivers on the size and resources hype. I was able to follow the docs with no issue, to use a multi-stage Docker build to make a native executable without GraalVM even being installed (I did have some issues with Gradle, they are clearly Maven-first). Startup is near-instant, even if you AREN'T using GraalVM, and resource use is low.
5. I never got as far with Micronaut in building native executables. And while the startup speed and resource use is lower than a Spring app, it isn't DRAMATICALLY lower. Quite frankly, I think they're in a "mushy middle" position. Not compelling enough to migrate away from Spring... but if you really DO need to go lighter than Spring, then there are better options.
It a nutshell, I might use Quarkus if I wanted to use Java to write a serverless function (or other such constrained context). For general microservices, I'd just continue to use Spring Boot, and wait for their next release or two to steal most of these innovations anyway.
Just reading the Quarkus docs now, I see they're using Hibernate. That was the one big problem I had working with Spring/Boot and I would personally avoid it although I don't have recommended replacement. My problem with JPA+Hibernate was that it was being clever (e.g. delaying operations, caching query templates) as well has creating different forms SQL vs JPQL with different limitations and gotchas.
You already like Micronaut and its docs. If not using Hibernate I'd say go for it. When I looked at it, it seemed like a more modern Spring.
You just create a wrapper for the handle (initialized) and inject it wherever you need.