Speed is important, but so is quality of results, especially when it comes to search. You can make something search blazingly fast, if it doesn't need to be accurate.
True! Here's a pull request to BEIR to compare Manticore with Elasticsearch in terms of relevance https://github.com/beir-cellar/beir/pull/92. Spoiler: in this test Manticore provides better relevance than Elasticsearch in average. Of course you can tune both further and Elasticsearch now has KNN which when combined with BM25 can give even better relevance. In general I would say for most users the results quality in terms of full-text relevance is about the same in Elasticseach and Manticore.