Why having more....
There are simply different philosophies to build db access. In the pascal world we have somehting like a standard >> the TDataset compatibilty << that provides a common programmatic as well as a reliable interface databournd components that rely on.
Everything beyond is a matter of taste ...
From my experience SQLDB is good ... many people also under UNIX find it very satisfactory. As long as you come along with them be happy.
In reallity honestly especially if you target with one .exe different databases you will very soon come to the point that you have to provide different SQL statements, have batch insert updates or not, transactions or not, have to store data offline, connection information provided by an infrastructure,.... different layering ... in reallity the componentlayer is something nice but not requried ... if you want to go beyond maybe you want to have a different level of abstraction (when building your own framework for data driven apps....), speed ...
ZEOS is very practicable and available for Delphi too. I think this is a major difference and said to origin form the ideas of JDBC ... whatever this means in the end ... feel free to find it out.
I kindly suggest to try to come along with what comes on board ...