Well MIK has more accurate key detection. Still no software is perfect, but MIK has an edge over Rekordbox and Serato in that regard. Also it can easily check the energy levels which is OKish and you can auto-tag mp3 tags easily.
Hence I like MIK a lot.
Also: The DDJ-RB + Rekordbox DJ is lightyears more advanced than any CDJ in production, so unless you want to downgrade or go back in time we discourage you to switch to CDJs from this setup. However the crappy displays in the overpriced CDJ2000 Nexus and Nexus2 will display key info that is in the mp3 key tag if setup correctly. So prolly wont work 50% of the time.