I just came back from a golf trip with 16 of my buddies to Sand Valley and Lawsonia Links.
First, Sand Valley Resort is incredible and with time to build more courses, it will certainly be one of the best golf resorts in the US. Is it better than Bandon? I am not sure as that is a tall order. However, both are so good that I will leave it to the overly analytical to decide.
How would I split up 10 rounds at Sand Valley and Mammoth Dunes - 5-5 (with Sandbox when time permits after any round). They are that even and that good. However, they do provide different things if you want to slightly adjust that ratio.
Sand Valley is a better (more natural feeling) walk and probably plays in a better setting. There is an incredibly large dune that dominates a north ridge on the back 9 and the 9th plays into a gorgeous area with a lake and fire pits to the south. The par 5s are really good and are probably the best holes on the course.
Mammoth Dunes likely wins a hole by hole match for most average retail golfers, which was most of my group. In fact, most of my group preferred Mammoth Dunes (even though I am really split). In fact, about 6 of them told me it was the most fun that they have ever experienced playing golf. Is it a true test of golf for the traditionalist - no. However, it is incredibly fun. I understand some criticizing it for its width, but I think most golfers like getting off the tee and just not being out of hole just after the first shot.
The Sandbox is a leisurely par 3. Yes, it is very short....to the point that it is almost as much of a putting course as a par 3 course. The simplest way I can put it - if you are keeping score, it isn't for you. It is designed for friends to have fun together after a round at Sand Valley or Mammoth Dunes and have bets on "closest to the pin" - whether from the tee or some crazy part of the green. I would say 90% of the groups have cooler bags of beer and 50% are listening to music. You can literally putt from tee to green on 12 of the 17 holes.
I also played Lawsonia Links. I enjoyed it. Nice golf course. However, don't be fooled by its name. It isn't close to a links golf course. In fact, if you aren't a high ball hitter, I can see you having a hard time with the golf course. It is worth seeing once, but don't put me in the camp who believe that it is in the same class as Sand Valley or Mammoth Dunes. IMHO, there is no comparison.