Solr vs ElasticSearch by Ryan Tabora.
Ryan evaluates Solr and ElasticSearch (both based on Lucene) in these categories:
- Foundations
- Coordination
- Shard Splitting
- Automatic Shard Rebalancing
- Schema
- Schema Creation
- Nested Typing
- Queries
- Distributed Group By
- Percolation Queries
- Community
- Vendor Support
As Ryan points out, making a choice between Solr and ElasticSearch requires detailed knowledge of your requirements.
If you are a developer, I would suggest following Lucene, as well as Solr and ElasticSearch.
No one tool is going to be the right tool for every job.