I've looked into this recently. There is no advantage to forcing the CDJ SPDIF output into 16 bit unless the output is feeding something that can't see 24 bit. At worst, the extra unused bits are getting padded if the pitch fader is at zero. At best, the pitch change and master tempo is being done in 24 bit domain instead of 16 and there is no disadvantage to that, only advantages. Now, if you played 24 bit files, having forced the SPDIF into 16 bit would be degrading. Sample rate would be a different situation, but the CDJs change to match the file played.