Comparing ZFS and HFS to FAT32 and NTFS is valid, but not quite the same. HFS+J, or Hierarchical File System Plus Journalled is the default file-system under OS X. It is something like 10-15 years old, maybe older if you take into account its earliest HFS roots. It is a pretty good FS (File System), but ZFS or Zettabyte File System, is much, much better. For one thing, it has a much higher storage limit than either NTFS or HFS+J, or really any other File System in the wild. The theoretical limit is so high that I honestly think that I will not see any drives that truly stress it within the next say.... 50 years.
Let me put it this way. I could give you a million dollars, and you could spend all that money on Terabyte hard drives. That is thousands of hard drives. Then suspending the fact that you can't hook all those up to a single system due to physical limitation, if you could, ZFS could handle it. Then when you booted into a ZFS based system, you would see 1 disk of that ridiculously large size, and the File Sytem can handle it. If you were to then remove a disk, or add it, you could go in the disk manager on the OS and tell ZFS to start or stop using a drive, and it would handle it. Moving your files off that drive (assuming there was sufficient free space) and pooling it onto others.
I unfortunately am not as familiar with the other FSs because before I never gave much of a hoot beyond which one was best for a certain application.
