They generally have enhancements to push initialisation to build-time and/or make them native image compatible.

Exactly that. E.g. in case of Hibernate ORM, the corresponding Quarkus extension will take care of having the persistence.xml being parsed at build time, registering entity properties for reflection in native binaries, making sure all needed resources are added to native binaries, etc.

They also curate the right set of matching (transitive) dependencies for each library, you just need to add the Hibernate ORM Quarkus extension, without having to think too much about versioning. Also they integrate different APIs: e.g. when having the Kafka Streams extension and the MicroProfile Metrics one, you'll automatically get metrics for your streaming pipeline.

Disclaimer: Working for Red Hat, contributing to Quarkus a bit (Kafka Streams and Debezium outbox pattern extensions).

Just about to put a substantial project into production using Quarkus. I would say the main advantages vs SB are:

* mostly uses standard javax/Jakarta/Eclipse etc APIs so code is relatively portable (in ~600 classes I found 8 quarkus imports)

* build time DI/weaving

* best dev-mode autoreloading I have seen

* in general, less Spring-y

* less reliance on classpath-searching and reflection voodoo, less weird shit breaking bc of dependency version conflicts

* stack traces and class names (https://gist.github.com/thom-nic/2c74ed4075569da0f80b) that fit within a human’s field of vision

* less overriding feeling of death by OOP

We started with Spring Boot, switched about halfway through and never looked back.

> mostly uses standard javax/Jakarta/Eclipse etc APIs

This is the selling point for me, never was a Spring fan.