One large RAID 6 or Two smaller RAID 5 arrays

[RealBeast]

I have a client that is very very poor at backups, and while I preach that RAID is NOT a backup solution, his just might be some of the time. I can set him up two 4 disk RAID 5 systems that are mirrored, or one RAID 6 with two hot disks. Which way to go?

 

[FireWire2]

RAID51, but

Ideally! a RAID5 or RAID1 and a remove-able archive HDD for off-side