Differences between DSST and GMAT / numerical integrations (J2 squared terms not implemented)
Propagation of LEO satellite orbit for long periods: differences from GMAT (about 0.02 degrees in inclination for 10 days propagation).
Detailed description and source code in the forum topic: https://forum.orekit.org/t/doubts-about-dsst-using-comparing-with-numerical-integration-and-gmat/1702/4