While it may be true that pictures of the three courses look similar in many respects, Ballyneal is built on significantly "choppier" terrain, where the dune peaks are much closer together. Actually the Ballyneal photos look quite different than these. Two architects with differing philosophies.
Dismal River is a private golf club. There are many membership categories, and some are quite reasonable.
I have seen all three courses. Sand Hills is terrific, as previously discussed here. Dismal River is a very large course laid out across a large area. That blowout bunker shown in the second photo is enormous, and extremely penal. Surprisingly, Dismal River will have more "quirky" features than either Ballyneal or Sand Hills. For instance, that windmill in the picture can come into play on the second shot of a short par 5. Not a bad idea, in my opinion. Also, from the back tees it will be exceptionally difficult. It's a very impressive project, and I expect it will succeed financially. However, it is a major pain in the ass to get there.
The gentleman who took us on the Dismal River tour mentioned the lead shaper, a well known guy who had worked for Tom Fazio and maybe Rees Jones in the past, but I can't recall his name.
Not only are shaping details and hole strategies important, walkability is a key feature. Sand Hills is a tough walk, and most everybody rides a cart there. Dismal River will be similarly or even more difficult to walk. It's not hillier than Sand Hills; the green to tee walks are a bit longer though.
Another difference: Dismal plans to use A4 bent grass on their greens. Ballyneal will use a proprietary mix of fescues, bents, and bluegrasses, and will probably keep its green speeds a little slower than the other courses. I believe Sand Hills uses A4 bent. When I played there, the greens were all world.
Ballyneal and Dismal River are considerably different. Both have their merits. If you are considering a trip out to see Dismal River, make sure to stop in Holyoke and see the great Ballyneal first.