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.