If you're performing in front of an audience then access speed is everything because dancers will quickly return to their seats if you have to wait 15 seconds for a floppy disk to load up the next settings. However the SD Card system in the Technics KN7000 is very quick and will hold settings for over 1800 songs.
As Microsoft have updated their operating systems so the process of transferring tracks (MP3s) to an SD Card has become impossible to operate, and it wasn't always all that clever anyway. I take Jan's point in that using a Gotek emulator enables tracks (MP3s) on a USB stick to be played instantaneously hopefully.
_________________________
Roger M