Ingest data through ElasticSearch (instead of AppSearch)

Hello,

We are using AppSearch but indexing in bulk was quite slow, so we decided to create engines based on Elasticsearch indexes.
The indexation is really much faster when indexing Elasticsearch indexes.

Do you see any drawback or difference (on the frontend, settings, on whatever) on indexing Elasticsearch indexes VS indexing AppSearch engines? Could we do both without noticing the difference ?

Thanks