I see a lot of ND fans happy about this, but then I remember how happy ND fans were when Carroll was named HC there. FIsher's brand could work well at USC if he brings in an established OC and gets out of the way. Del Rio had success in the NFL too and I wouldn't completely write him off from being successful at USC.
Of the two I think I'd rather Fisher since he's already 60 and might not want to put in all of the work on the recruiting trail.