The splunk_instrumentation.log file is the least helpful in troubleshooting a crash, because it contains information about the Splunk Instrumentation feature, which collects and sends usage data to Splunk Inc. for product improvement purposes. This file does not contain any information about the Splunk processes, errors, or crashes. The other options are more helpful in troubleshooting a crash, because they contain relevant information about the Splunk daemon, the standard error output, and the crash report12

1: https://docs.splunk.com/Documentation/Splunk/9.1.2/Troubleshooting/WhatSplunklogsaboutitself#splunk_instrumentation.log  2: https://docs.splunk.com/Documentation/Splunk/9.1.2/Troubleshooting/WhatSplunklogsaboutitself#splunkd_stderr.log