According to the Splunk documentation1, one of the benefits of search head clustering is the automatic replication of user knowledge objects, such as dashboards, reports, alerts, and tags. This ensures that all cluster members have the same set of knowledge objects and can serve the same search results to the users. The other options are false because:

Allowing indexers to maintain multiple searchable copies of all data is a benefit of indexer clustering, not search head clustering2.

Input settings are not synchronized between search heads, as search head clusters do not collect data from inputs. Data collection is done by forwarders or independent search heads3.

Fewer network ports are not required to be opened between search heads, as search head clusters use several ports for communication and replication among the members4.