For any searches that need to use some kind of keyword search, fuzzy/partial text matching via tokensiation/stemming, case insensitive comparison, range checks, date/time checks, content full text search.... you need SOLR. Metadata search against the DB only supports a small subset of the Alfresco search capabilities and queries need to be specifically written to be supported (most query examples you find on the net typically don't support it).
I have to correct Jeff in a small detail: metadata queries against the DB can be very fast and even faster than SOLR queries (with their HTTP overhead), but you need the right use case, content model and a reasonably well managed / maintained database (statistics; query plan reoptimisation enabled; ideally even some custom indices for common DB search use cases). But due to spotty / non-existent documentation on the criteria for "suitable use cases" / "good performance", most people do end up not being happy with the performance...
Also, if you just want to test without SOLR you do not need to disable / stop it. Simply set your default query consistency to TRANSACTIONAL and SOLR will not be called for any searches unless code specifically allows it to be by overriding the default setting.
