To whom it may concern: the "solr" extension is more complex to configure. It requires on the server: a Java development Kit (JDK), a Tomcat server, and solr itself. Quite a task to setup and configure for the non-java programmer/admin, and not for the uninitiated. - Moreover there are elaborate dependencies with other typo3 extensions (check the "version matrix) on their website.
– knbAug 23 '16 at 12:23