In RAID 1, all changes are automaticaly send to both drives by the controller so both drives are ALWAYS in sync. If you loose one drive, any software reading from or writing to the drive is unaware of the failure so you don't have an outage caused by hardware failure.
Ghost is just backup software and the image it generates is fixed in time. Any subsequent changes made to the drive aren't part of your backup. Also, any drive you want to back up has to be taken off line while the backup is being done (the drive can't be in general use while you're making your backup).
The one thing apps like Ghost are good for is for when you want a backup and DON'T CARE about any further changes to the information on a drive (e.g. you want to have a backup from a "known good point"). Back when I was a sys admin, I would ghost a server's drives before I would install a MS service pack. That way, if the service pack broke something unexpectedly, all I had to do was restore from my Ghost image. Ghost is also useful when your boss says we're getting 40 new PCs and he wants them configured EXCATLY the same. All you have to do is configure one box the way you want it, and then clone the drive to the other 39 PCs.
I'm not familiar with Fileback so I can't offer any advice about it.
Hope this helps.
Dave
Edit: added more info
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