What is the difference between DDJ-SB or DDJ-SB2 and DDJ-RB?

DDJ-SB and DDJ-SB2 are models optimized for DJ performances using Serato DJ. Serato DJ intro is included, and the units are equipped with operation interfaces in an optimal layout for operating it. Whereas, DDJ-RB 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.