I'm a Ballyneal member, so you're forewarned ;-)
I've played Ballyneal three times (it opened for limited member play in October) and Sand Hills approximately five times. I haven't seen Dismal.
The land forms at the two courses are very different from each other. The Ballyneal dunes are taller, rougher, more choppy than those at Sand Hills. (I've asked if the dunes at Ballyneal are younger geologically than those at Sand Hills, but I haven't received a definitive answer.) The 18th hole at Ballyneal, however, is very reminiscent of the land forms at Sand Hills -- gentle, almost elegant.
Both courses are very, very wide (they have to be with the wind), with memorable hole after memorable hole. The green sites at both are varied in size and completely original. I think you need to putt well and read the greens well at both. A couple of the Ballyneal greens are really wild with amazing undulation.
I think Ballyneal will yield more uneven fairway lies than Sand Hills.
Ballyneal is walking-only, and use of caddies will be strongly encouraged. It's hoped that the lack/absence of cart traffic will help in preserving its fescue-dominated playing surface.
Sand Hills feels more remote to me than Ballyneal.
I said this in February: some will prefer Ballyneal and some will prefer Sand Hills. If you enjoy wild terrain like that generally found on Irish links, I think you will prefer Ballyneal. If you fancy Scottish links, then you'll go for Sand Hills. Rolling Stones/Beatles, Beethoven/Mozart -- Ballyneal/Sand Hills will be one of those types of debates.