Are there any SMEs that have worked with both OpenSearch (the fork) and ElasticSearch? Are there significant differences?
I know the AWS fork had the big difference back then of having RBAC built into their Kibana portion.
(and before OpenSearch, the AWS-managed ElasticSearch absolutely hurt the ElasticSearch brand because of all of the issues Amazon created - it couldn't even rebalance shards, let alone add new nodes or switch to larger nodes without a blue-green deployment)
There are some Elasticsearch features that were part of X-Pack (their commercial offering) so aren't included in the OpenSearch fork. Some of those features are really nice to have and make life much easier; the enrich ingest processor is something I really miss in OpenSearch.
The biggest differences are in the tooling around Elasticsearch. All the observability stuff, the SIEM features, various integrations, and now the AI fluff. I've worked with clients in different sectors and - aside from the observability stuff (which is really nice) - none have had an appetite for any of that.
The OpenSearch team is doing some really cool stuff and the project has come a long way. I'm sure it'll continue to improve. It has a very loyal customer base and even has its own annual event; OpenSearchCon 2024 is next month!
Elasticsearch hands down for this area.
The exception to this might be vector search, which is a relatively new feature that was implemented on both sides post fork. Lots of users want/need this. And both Elastic and Opensearch provide independent implementations with very similar feature sets. Both build on what Apache Lucene offers on this front. So there isn't a massive difference between the two. But I would give the advantage to Opensearch here since its implementation offers a bit more beyond just the Lucene support.
Kibana had a lot of closed source components before the fork already and Amazon fork of that is a bit more limited. But notably Amazon indeed re-implemented the security layer (before the fork actually), which on the Elastic side is a bit of a dumpster fire of complexity. In general I'm not impressed with the product from a usability point of view. Either on the Elastic or the Opensearch side. But the Elastic version is arguably a bit richer in features.
Some notable recent changes there include trying to introduce a new query language based on SQL and the whole fleet ecosystem (an agent based system) to get logging and other data into Elasticsearch. I don't think either is getting a lot of traction because of the licensing.