The second hole at Riviera is enormously difficult, as you have said. Plays very long, significantly uphill, with a very sloped green. A traightforward backbreaker. Was #2 at Riviera ever considered a par 5?
The second hole at Sand Hills is easier, since it's shorter. I have mixed feelings about this hole. I find the blindness of the tee shot very disorienting. The landing area is not that wide, perhaps averaging 50 yards, and I often end up in the native grasses left of the golf course. In my experience, a full 20-30% of the tee shots end up there. If I played there regularly, I would improve, after determining a good aiming point and having greater confidence about what to do.
I agree that the second green is outstanding. I remember two brilliant short game plays in my time there. One time, Ted Moore got up and down from just off the back left to a front left pin by playing way out towards the back right of the green. A 15 second play, if you will. The other time, I got up and down to the back right shelf from in front of the green by pitching it up onto the short grass area long and right, and letting it trickle past the pin. I had to make an 8 footer to do it, but I was so fully engaged, I just had to make it, and I did.
Wow, what a tough call to say which is better. Riviera's second is mundane by comparison, whereas Sand Hills is nothing if not exciting. I hate lost balls in the native; I love the approach shot and the green. I'll also say Sand Hills wins by a nose.
Sand Hills #2 wins, all square.
(JK: I hope this OK for me to play along, since I know both courses quite well. I'm really enjoying this.)