I have both diamonique and absolute. In general, if you are talking about a round stone, in 1 ct size, both are equally good. In other shapes, some stones seem to be better than others. But remember, only diamonique has the lifetime warranty on the stone.
Consider the quality of the setting as well as the stone.
Moissanite is in a totally different price range. And remember, it's a man made stone also.