Raymond Fox wrote:
. . .
But now I'm wondering whether it would have been better to have designated the second drive as a Time Machine backup drive?
Yes, in several ways.
For one thing, if I accidentally erased a file, I could retrieve it if the second disk was a Time Machine backup disk, but I think it'd be gone forever with a RAID set.
Also, Lion won't put a Recovery HD on a RAID set (just why isn't clear).
If you're thinking of using FileVault2, it won't do that, either.
Any input on which method of backing up I should choose?
If you're unsure about different types of backups, see Time Machine vs. Clones and Archives.