Hi Shalin,
thanks for your e-mail.
My dilemma is which one to use between BASE-X and EXIST-DB.
Maybe it's not too bad: It hardly takes any time to run and play around with BaseX, so I would recommend you to simply try it and see if it "feels good"! If you want to get to know the GUI, which allows you to create databases or run queries, it's sufficient to download and double-click the core package [1]. This file also contains the full client/server architecture [2].
You will discover that BaseX is very compact. It can be used out of the box (without installation) and completely embedded in your Java code. Our Wiki contains some more information on how to retrieve data from Java clients [3].
A W3C test summary reads using base-x is efficient.
We are indeed spending much time to get as compliant as possible with the official spec. XQuery 3.0 is now fully supported as well [4], and we are already have some support for upcoming XQuery 3.1 features, such as maps (arrays will be added as soon as the inofficial specs get more stable).
BaseX also supports XQuery Full Text and the Update Facility (see [5,6] for the test results).
I will be highly obliged to you if you can give some more concrete points that insist on using base-x so that I can make a fair decision.
As you already indicated, there is no killer argument for using either BaseX or eXist-db, as the systems are simply too different (even if both of them can create databases and run XQuery ;).
Hope this helps; feel free to ask more questions, Christian
[1] http://basex.org/products/download/ [2] http://docs.basex.org/wiki/Startup [3] http://docs.basex.org/wiki/Developing [4] http://docs.basex.org/wiki/XQuery_3.0 [5] http://dev.w3.org/2007/xpath-full-text-10-test-suite/PublicPagesStagingArea/... [6] http://dev.w3.org/2007/xquery-update-10-test-suite/results/XQUTSReportSimple...