Should be identical.
Only difference would be in font differences or different font verions, or font formats.
There is no significant difference, but they will not be bit-for-bit identical.
For instance, the INDD file format records which version and platform of InDesign created the file, so that small piece of information will certainly differ. Also, historically, when Macs used non-Intel processors with different byte order, ID may have stored some numbers in reversed byte order. But since everything is Intel now, that's not an issue.
In any case, there is 100% compatibility between both platforms. Mac ID can read Windows ID and vice versa.