For a carry gun? I'm very close to ordering a Springfield XD40 compact (3" barrel) and I think it would be good to splurge extra for night sights, right now I have no night-sighted guns. So, the cost is the same for the Heine "8" sights (dot over a dot) or for the Trijicon 3-dot night sights.
Is it just a matter of personal preference which to get, if one gets night sights? I don't know that it would matter much to me, although I'm leaning towards 3-dot to be like a number of my other pistols.