<p>I am creating a desktop app in Delphi and plan to use an embedded database.  I've started the project using SQlite3 with the DISQLite3 library. It works but documentation seems a bit light.  I recently found Firebird (yes I've been out of Windows for a while) and it seems to have some compelling features and support.</p>

<p>What are some pros and cons of each embedded db?  Size is important as well as support and resources.  What have you used and why?</p>

I'm using Firebird 2.1 Embedded and I'm quite happy with it.I like the fact that the database size is practically unlimited (tested with > 4 GB databases and it works) and that the database file is compatible with the Firebird Server so I can use standard tools for database management and inspection. Distribution consists of dropping few files in your exe folder.
Simultaneous access from multiple programs is not supported but simultaneous access from multiple threads is (as long as you ensure that only one 'connect' operation is in progress at any given moment).