For very small datasets, Whoosh is fine. For anything larger than 'site search' on a website that has no UGC, you're much better off with SOLR (or ES, Xapian or Sphinx - whatever your poison).
When document counts get into the hundreds you see orders of magnitude faster queries with SOLR (etc), not to mention much more sophisticated querying options.
> Once my site grew larger than 50 mb of text queries started slowing things down. Indexing (python, single threaded) took a while and the larger the index the slower the queries were returned.
I think this makes it pretty clear. Not sure how much more explanation you need.
