NTFS, both can read but MAC won't be able to write on it, unless u installed MacFUSE/NTFS-3G on it
FAT32, Both can read and write, but a single file can't be larger than 4GB
HFS+, Windows need software to use it
That's why i go for NAS, as i don't need to worry about the format and it can be used by more than 1 computer at a time