It's easy to get up and running, and I've grown to appreciate the emphasis on stable, mature libraries in Dropwizard compared to some of the more bleeding edge libraries that I've fought with in other "opinionated" Java frameworks that try to approximate the RoR experience.
Dropwizard gives you the option of using either JDBI or Hibernate for an ORM. My suggestion would be to go with Hibernate, even though it's a beast and you will waste time deciphering cryptic error messages and hunting down crippling N+1 select performance problems. Even with those issues, I feel that Hibernate is worth using, as even on small projects it can save you from writing thousands of lines of monotonous database access code.
Not sure how many Grails 2.x systems out there have been upgraded to Grails 3.x, or how many new Grails systems have been started in version 3.x. I don't think it's many though, which suggests a general decline in Grails use.
That said, not sure I'd pick it for simple side-projects. Part of the benefit here is how it works for a large dev team, with a large codebase, etc.
Very elegant introduction to Java Land, it uses Java EE 7 and by default two servers Payara or Wildfly(around 100MB).