On ElasticSearch you have to update the whole document, no commands to manipulate them. You don't have commands like: $set, $addToSet, $pop, etc..

You need to have a good understanding of how tokenizers and analyzers work to be able to create good results for your data. I have difficulties matching documents with the exact title being searched for. On MongoDB that just works, on ElasticSearch you need to configure it.

ElasticSearch has some advantages and MongoDB others. I think they are great together. One for storage and the other for searching.