@wozza.lowe if your search use case is just matching simple text like exact terms or phrase matches with basic sorting MongoDb full text search will work fine. MongoDb supports index time boosting of the fields.
If you need support of fuzzy search (matching records even with typos in search query), additional things like search time boosting, complex sorting things based on decay functions, sort builders, etc.. then i would say go with Elastic Search.