Comparing native XML database (NXD) and relational DBMS solutions is close to comparing apples and oranges. Both are spherical fruit, but they have very different flavors, applications, and characteristics. RDBMS has been around for a long time and is much more established than NXD; as a result, there is less collective knowledge around NXD and its implementations. RBMS solutions are practically ubiquitous and have a number of different implementations, both open-source and proprietary. Tables are normalized and typically in a fact/dimension model or star schema.
On the other hand, comparative NXD solutions rely on containers and documents in a simple tree structure. Complex joins and queries that are allowable in RDBMS are typically more difficult in NXD (Pavlovic-Lazetic, 2007). One area that NXD shows promise is in Web-enabled data warehousing (Salem, R., Boussaïd, O., & Darmont, J., 2013). Bringing multiple sources of unstructured and structured data together in an Active XML Repository addresses data heterogeneity, distribution, and interoperability issues.
A typical RDMBS implementation for business is a data warehouse in which structured data from various systems of record are brought into a common area and reconciled. These other systems of record may include proprietary relational database systems, mainframe non-relational databases, data exported to delimited formats, et cetera. A data dictionary may be maintained and reconciliation policies may be drawn up by a central data governance board. The output from this data warehouse allows users from different divisions using different systems of record to understand a common organization-wide data taxonomy.
One possible NXD solution involves an IoT data environment. Imagine a number of environmental sensors (e.g., temperature, humidity, pressure) being read on regular intervals and pushed to a central web location. In a typical XML tree structure, readings from each sensor or central controller (handling multiple sensors) could be placed in an XML document. This data does not require complex joins, and is much better suited for a NXD solution.
Pavlovic-Lazetic, G. (2007). Native XML databases vs. relational databases in dealing with XML documents. Kragujevac Journal of Mathematics, 30, 181-199.
Salem, R., Boussaïd, O., & Darmont, J. (2013). Active XML-based web data integration. Information Systems Frontiers, 15(3), 371-398.