Currently, I backup my system to two external hard drives, which requires two separate backup operations.  I keep one drive onsight and the other offsight.  The process takes a few hours.  The backups are not exactly equal, since some files change during the first backup operation since it takes so long, but this isn't really a big issue.

My thought is to get a RAID 1 system and only do a single backup operation, letting the RAID system handle making the second backup to the other drive.  I would then keep one drive onsight and the other offsight.  This would cut my backup time in half, since I only need to do one operation, and it would give me two exact equal backups.  Granted, the drives in a RAID system are internal and not really meant for transportation, but that aside, is there a reason I should not go with this setup and keep on with my separate external drives and two backup method?