I've seen a handful of Nicklaus layouts, several of them "signature designs," including Sherwood CC, Diablo Grande-Legends, Ruby Hill CC, Dismal River, and Palmilla.
Ruby Hill is pretty bland. The others are decent layouts, but perhaps not quite as good as they might have been relative to the sites IMHO. I find that his courses look pretty and play conventionally. I would prefer a few more subtleties around the greens to allow for imaginative recovery play. Average design rating at a B or B+
I haven't really had the chance to sample Fazio's original work -- I've only played he renovations at The Finley Course (UNC) and Edgewood. I'd love to sample Victoria National first and foremost.
Still, if I were investing my own money in a project, and hoping to profit, I'd be inclined to hire one of these two firms purely for their name recognition and consistently good, if not great, track records. Nicklaus' design career is the reason we now know the names of people like Doak, Hanse, etc.