I have used Elasticsearch. Elastic is the older solution, so it tends to be not as well-documented or structured in the documentation as the Microsoft solution. 

The APe Syntax is somewhat convoluted because it's older. Whereas Microsoft had the opportunity to do something correctly from day one.

We also use AWS. The services that we are using are more stable in Azure. We need stability, and Azure is a very stable solution.

Azure Search came as an added value when we purchased a full Microsoft license. We were then given the opportunity to switch to Azure so we decided to work with it.

Prior to using Azure Search, most of the applications that I created used on-premise Lucene.NET solutions. I decided to transition to Azure Search to leverage the scalability of the cloud and the additional faceting and scoring capabilities.