The direct player in the Korgs will be the best bet, unless you want a random play option. That's one thing I miss bout the Yamaha s950 - the MP3 player had a shuffle feature, so when I used a folder for break tunes, it was varied each time. The waitresses appreciated it!
One point - the 900 does not put out the same volume that the other models did - maybe it's a mastering thing, but the MP3 files are quieter than the smfs in my unit.