Hello!
What exactly do you mean by “comparing the store result”? Do you mean the size of the data on-disk after ingestion?
In that case you could do a single-node install on the same server using the same (or comparable) settings for both instances and then compare the index size using the api for example.
Also it seems like you only want to ingest and store the log of those services and I don’t think there are any real downsides to choosing OpenSearch over Elasticsearch.
BR
Andreas