Difference in disk usage MS DOS vs Extended Journaled
FAT32 on a large drive has a larger block size that HFS+. This means that the small amount of "wasted" space per file is larger and therefore the same files will take up more space. It's because FAT32 only uses 28 bits for it's cluster index while HFS+ can use it's entire 32 bits.

One of the marvelous things about Steve Wozniak is that he designed a disk system for the Apple ][ that was both efficient, extensible and easily implemented and the original Macintosh File System (MFS) was built on top of his work after Wendell Sanders created a single chip implementation of Woz's drive controller the IWM chip. It was replaced by the Hierarchical File System (HFS) and then HFS+, otherwise known as Macintosh Extended.