What is the difference between the DDJ-SR and DDJ-RR?

DDJ-SR is a model optimized for DJ performances using Serato DJ. Serato DJ is included, and the unit is equipped with optimal operation interfaces for operating it. Whereas, DDJ-RR is a model optimized for DJ performances using rekordbox dj. rekordbox dj is included, and the unit is equipped with optimal operation interfaces for operating it. In addition, DDJ-RR has input terminals for connecting external players, and functions such as needle search to quickly play back from any point by simply touching.