The DITA Open Toolkit (DITA-OT) provides a command-line tool for users with little knowledge of Ant. The command-line tool supports a subset of the parameters that are available to the Ant builds.
The command-line tool is a wrapper around the Ant interface; it takes the simplified parameters as input, converts them to Ant parameters, and then runs an Ant build. The Ant parameters that are passed to the DITA-OT are saved to the property.temp file that is written to the output directory.
For individual builds, the additional Java overhead is minimal, but for repeated or server-based builds, the extra memory usage might become an issue. Applications that embed the toolkit should invoke Ant directly.