I've had some issues with exFAT recently.  I have a 32GB USB3 thumbdrive which was formatted in exFAT.  I took it to work to update my music folder at work where all of the computers are XP Pro SP3.  According to Wikipedia, SP3 should support exFAT but when I inserted the thumbdrive, it popped up saying "this disk requires formatting".  I tried a couple of machines but no joy.
As a result I've gone back to NTFS.  Out of curiosity I did run CDM on both file systems and the scores were the same, give or take a MB or two.