What are the advantages of using synonyms at index time vs expanding at query time? In what case would you use both?
There's a very good write-up at http://nolanlawson.com/2012/10/31/better-synonym-handling-in-solr/ … I remembered that one, because I had the same question recently, and I found that via Google *wink wink*.
Basically, there's a huge difference between both, and you may need to use both in the end, depending on what you're trying to achieve.