Problem in copying folders to exFat drive(external hd) in ML

Hello experts,

I recently switched to macbook from windows. I have mountain lion installed. I want to share my data with windows laptop. Based on my research on internet, i thought using exFat on external drive was the best way to share data between mac and windows. I copied around 25 gb of data from mac to exfat partition. I did not get any error in copying but when i opened it on windows, only 20 gb of data was copied. When i verifed it with original data, i found that many folders were not copied leading to size difference.

Is this a bug or some known limitation? May be wrt to path lenght?

None of my file was more than 4 gb.

Thanks for the help?