One warning about Plucene: it's slow. I'm working on mailbox indexer (to be released real soon now) which can use swish-e or Plucene as index, and as far as real-life examples go, Plucene is just too slow.

If your document collection isn't tiny (e.g. couple of hundred documents) you might want to use swish-e. On the other hand, Plucene query syntax and ability to add documents to index on the fly are good reasons to use it anyway.