David;
I think it's an interesting question I tried to address on another related thread, but if you're actually talking about driving it and holding the green, then the 10th at Riviera seems tougher simply because the fronting bunker there prevent the run up drive across most of the green.
It's also shallower in real terms from the tee, although the 12th at RC plays about 1/2 it's real depth from that distance.