CDJ-2000 NXS2 Player # and DJM-900 NXS2 Channel # Match

Hi, there - been digging into the manuals of the the CJDs, DJM and Rekordbox, and I keep reading that it is recommended to set set the CDJ player ID to match the channel on the DJM mixer to maximize the features of the various products. I have my CDJs hooked up to channels 2 and 3 of the mixer, and have them set as player ID 2 and 3. 

Can someone please explain what the benefits are in doing so - and what such features may be? 

Thank you,

Ivan