Are performance improvements by splitting a single Splunk instance into one search head and one indexer on their own servers?

Currently, I have a combined instance where the search head and indexer are sitting on the same box. The documentation does indicate that performance improvements will be made by splitting that centralized deployment into one search head and one indexer each on their own servers. (Look at the Summary of Performance Recommendations document) Is that the case? Or do you need to go to one search head with at least two different indexers? Thanks.